This is a note to let you know that I've just added the patch titled
x86/sev: Don't use cc_platform_has() for early SEV-SNP calls
to the 5.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-sev-don-t-use-cc_platform_has-for-early-sev-snp-calls.patch
and it can be found in the queue-5.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From cdaa0a407f1acd3a44861e3aea6e3c7349e668f1 Mon Sep 17 00:00:00 2001
From: Tom Lendacky <thomas.lendacky@xxxxxxx>
Date: Tue, 23 Aug 2022 16:55:51 -0500
Subject: x86/sev: Don't use cc_platform_has() for early SEV-SNP calls
From: Tom Lendacky <thomas.lendacky@xxxxxxx>
commit cdaa0a407f1acd3a44861e3aea6e3c7349e668f1 upstream.
When running identity-mapped and depending on the kernel configuration,
it is possible that the compiler uses jump tables when generating code
for cc_platform_has().
This causes a boot failure because the jump table uses un-mapped kernel
virtual addresses, not identity-mapped addresses. This has been seen
with CONFIG_RETPOLINE=n.
Similar to sme_encrypt_kernel(), use an open-coded direct check for the
status of SNP rather than trying to eliminate the jump table. This
preserves any code optimization in cc_platform_has() that can be useful
post boot. It also limits the changes to SEV-specific files so that
future compiler features won't necessarily require possible build changes
just because they are not compatible with running identity-mapped.
[ bp: Massage commit message. ]
Fixes: 5e5ccff60a29 ("x86/sev: Add helper for validating pages in early enc attribute changes")
Reported-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 5.19.x
Link: https://lore.kernel.org/all/YqfabnTRxFSM+LoX@xxxxxxxxxx/
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/sev.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -701,7 +701,13 @@ e_term:
void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
unsigned int npages)
{
- if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+ /*
+ * This can be invoked in early boot while running identity mapped, so
+ * use an open coded check for SNP instead of using cc_platform_has().
+ * This eliminates worries about jump tables or checking boot_cpu_data
+ * in the cc_platform_has() function.
+ */
+ if (!(sev_status & MSR_AMD64_SEV_SNP_ENABLED))
return;
/*
@@ -717,7 +723,13 @@ void __init early_snp_set_memory_private
void __init early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
unsigned int npages)
{
- if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+ /*
+ * This can be invoked in early boot while running identity mapped, so
+ * use an open coded check for SNP instead of using cc_platform_has().
+ * This eliminates worries about jump tables or checking boot_cpu_data
+ * in the cc_platform_has() function.
+ */
+ if (!(sev_status & MSR_AMD64_SEV_SNP_ENABLED))
return;
/* Invalidate the memory pages before they are marked shared in the RMP table. */
Patches currently in stable-queue which might be from thomas.lendacky@xxxxxxx are
queue-5.19/x86-sev-don-t-use-cc_platform_has-for-early-sev-snp-calls.patch
