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109 lines
4.5 KiB
Diff
109 lines
4.5 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Mon, 6 Feb 2023 10:03:20 -0500
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Subject: [PATCH] ieee1275: request memory with ibm,
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client-architecture-support
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On PowerVM, the first time we boot a Linux partition, we may only get
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256MB of real memory area, even if the partition has more memory.
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This isn't enough to reliably verify a kernel. Fortunately, the Power
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Architecture Platform Reference (PAPR) defines a method we can call to ask
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for more memory: the broad and powerful ibm,client-architecture-support
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(CAS) method.
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CAS can do an enormous amount of things on a PAPR platform: as well as
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asking for memory, you can set the supported processor level, the interrupt
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controller, hash vs radix mmu, and so on.
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If:
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- we are running under what we think is PowerVM (compatible property of /
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begins with "IBM"), and
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- the full amount of RMA is less than 512MB (as determined by the reg
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property of /memory)
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then call CAS as follows: (refer to the Linux on Power Architecture
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Reference, LoPAR, which is public, at B.5.2.3):
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- Use the "any" PVR value and supply 2 option vectors.
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- Set option vector 1 (PowerPC Server Processor Architecture Level)
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to "ignore".
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- Set option vector 2 with default or Linux-like options, including a
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min-rma-size of 512MB.
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- Set option vector 3 to request Floating Point, VMX and Decimal Floating
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point, but don't abort the boot if we can't get them.
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- Set option vector 4 to request a minimum VP percentage to 1%, which is
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what Linux requests, and is below the default of 10%. Without this,
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some systems with very large or very small configurations fail to boot.
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This will cause a CAS reboot and the partition will restart with 512MB
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of RMA. Importantly, grub will notice the 512MB and not call CAS again.
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Notes about the choices of parameters:
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- A partition can be configured with only 256MB of memory, which would
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mean this request couldn't be satisfied, but PFW refuses to load with
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only 256MB of memory, so it's a bit moot. SLOF will run fine with 256MB,
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but we will never call CAS under qemu/SLOF because /compatible won't
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begin with "IBM".)
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- unspecified CAS vectors take on default values. Some of these values
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might restrict the ability of certain hardware configurations to boot.
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This is why we need to specify the VP percentage in vector 4, which is
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in turn why we need to specify vector 3.
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Finally, we should have enough memory to verify a kernel, and we will
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reach Linux. One of the first things Linux does while still running under
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OpenFirmware is to call CAS with a much fuller set of options (including
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asking for 512MB of memory). Linux includes a much more restrictive set of
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PVR values and processor support levels, and this CAS invocation will likely
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induce another reboot. On this reboot grub will again notice the higher RMA,
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and not call CAS. We will get to Linux again, Linux will call CAS again, but
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because the values are now set for Linux this will not induce another CAS
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reboot and we will finally boot all the way to userspace.
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On all subsequent boots, everything will be configured with 512MB of RMA,
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so there will be no further CAS reboots from grub. (phyp is super sticky
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with the RMA size - it persists even on cold boots. So if you've ever booted
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Linux in a partition, you'll probably never have grub call CAS. It'll only
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ever fire the first time a partition loads grub, or if you deliberately lower
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the amount of memory your partition has below 512MB.)
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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(cherry picked from commit d5571590b7de61887efac1c298901455697ba307)
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---
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grub-core/kern/ieee1275/init.c | 13 +++++++++++++
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1 file changed, 13 insertions(+)
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diff --git a/grub-core/kern/ieee1275/init.c b/grub-core/kern/ieee1275/init.c
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index 8ce1a0f09ee..13e8a5b4bb8 100644
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--- a/grub-core/kern/ieee1275/init.c
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+++ b/grub-core/kern/ieee1275/init.c
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@@ -850,6 +850,19 @@ grub_claim_heap (void)
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}
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#endif
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+#if defined(__powerpc__)
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+ if (grub_ieee1275_test_flag (GRUB_IEEE1275_FLAG_CAN_TRY_CAS_FOR_MORE_MEMORY))
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+ {
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+ grub_uint64_t rma_size;
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+ grub_err_t err;
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+
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+ err = grub_ieee1275_total_mem (&rma_size);
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+ /* if we have an error, don't call CAS, just hope for the best */
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+ if (err == GRUB_ERR_NONE && rma_size < (512 * 1024 * 1024))
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+ grub_ieee1275_ibm_cas ();
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+ }
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+#endif
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+
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grub_machine_mmap_iterate (heap_init, &total);
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}
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#endif
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