diff options
| author | Ashwin Dayanand Kamat <ashwin.kamat@broadcom.com> | 2023-11-29 11:40:29 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-11-30 10:23:12 +0100 |
| commit | 27d25348d42161837be08fc63b04a2559d2e781c (patch) | |
| tree | c4a012b827bed4e58d81241da4f5e4ecc6d70234 /arch | |
| parent | Linux 6.7-rc3 (diff) | |
| download | linux-27d25348d42161837be08fc63b04a2559d2e781c.tar.xz linux-27d25348d42161837be08fc63b04a2559d2e781c.zip | |
x86/sev: Fix kernel crash due to late update to read-only ghcb_version
A write-access violation page fault kernel crash was observed while running
cpuhotplug LTP testcases on SEV-ES enabled systems. The crash was
observed during hotplug, after the CPU was offlined and the process
was migrated to different CPU. setup_ghcb() is called again which
tries to update ghcb_version in sev_es_negotiate_protocol(). Ideally this
is a read_only variable which is initialised during booting.
Trying to write it results in a pagefault:
BUG: unable to handle page fault for address: ffffffffba556e70
#PF: supervisor write access in kernel mode
#PF: error_code(0x0003) - permissions violation
[ ...]
Call Trace:
<TASK>
? __die_body.cold+0x1a/0x1f
? __die+0x2a/0x35
? page_fault_oops+0x10c/0x270
? setup_ghcb+0x71/0x100
? __x86_return_thunk+0x5/0x6
? search_exception_tables+0x60/0x70
? __x86_return_thunk+0x5/0x6
? fixup_exception+0x27/0x320
? kernelmode_fixup_or_oops+0xa2/0x120
? __bad_area_nosemaphore+0x16a/0x1b0
? kernel_exc_vmm_communication+0x60/0xb0
? bad_area_nosemaphore+0x16/0x20
? do_kern_addr_fault+0x7a/0x90
? exc_page_fault+0xbd/0x160
? asm_exc_page_fault+0x27/0x30
? setup_ghcb+0x71/0x100
? setup_ghcb+0xe/0x100
cpu_init_exception_handling+0x1b9/0x1f0
The fix is to call sev_es_negotiate_protocol() only in the BSP boot phase,
and it only needs to be done once in any case.
[ mingo: Refined the changelog. ]
Fixes: 95d33bfaa3e1 ("x86/sev: Register GHCB memory when SEV-SNP is active")
Suggested-by: Tom Lendacky <thomas.lendacky@amd.com>
Co-developed-by: Bo Gan <bo.gan@broadcom.com>
Signed-off-by: Bo Gan <bo.gan@broadcom.com>
Signed-off-by: Ashwin Dayanand Kamat <ashwin.kamat@broadcom.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/1701254429-18250-1-git-send-email-kashwindayan@vmware.com
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/sev.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index 70472eebe719..c67285824e82 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -1234,10 +1234,6 @@ void setup_ghcb(void) if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) return; - /* First make sure the hypervisor talks a supported protocol. */ - if (!sev_es_negotiate_protocol()) - sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ); - /* * Check whether the runtime #VC exception handler is active. It uses * the per-CPU GHCB page which is set up by sev_es_init_vc_handling(). @@ -1255,6 +1251,13 @@ void setup_ghcb(void) } /* + * Make sure the hypervisor talks a supported protocol. + * This gets called only in the BSP boot phase. + */ + if (!sev_es_negotiate_protocol()) + sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ); + + /* * Clear the boot_ghcb. The first exception comes in before the bss * section is cleared. */ |