On 5/6/25 13:35, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.ka...@amd.com>
>
> When the shared pages are being made private during kdump preparation
> there are additional checks to handle shared GHCB pages.
>
> These additional checks include handling the case of GHCB page being
> contained within a huge page.
>
> The check for handling the case of GHCB contained within a huge
> page incorrectly skips a page just below the GHCB page from being
> transitioned back to private during kdump preparation.
>
> This skipped page causes a 0x404 #VC exception when it is accessed
> later while dumping guest memory during vmcore generation via kdump.
>
> Correct the range to be checked for GHCB contained in a huge page.
> Also ensure that the skipped huge page containing the GHCB page is
> transitioned back to private by applying the correct address mask
> later when changing GHCBs to private at end of kdump preparation.
>
> Fixes: 3074152e56c9 ("x86/sev: Convert shared memory back to private on
> kexec")
> Cc: sta...@vger.kernel.org
> Signed-off-by: Ashish Kalra <ashish.ka...@amd.com>
Reviewed-by: Tom Lendacky <thomas.lenda...@amd.com>
> ---
> arch/x86/coco/sev/core.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
> index d35fec7b164a..30b74e4e4e88 100644
> --- a/arch/x86/coco/sev/core.c
> +++ b/arch/x86/coco/sev/core.c
> @@ -1019,7 +1019,8 @@ static void unshare_all_memory(void)
> data = per_cpu(runtime_data, cpu);
> ghcb = (unsigned long)&data->ghcb_page;
>
> - if (addr <= ghcb && ghcb <= addr + size) {
> + /* Handle the case of a huge page containing the GHCB
> page */
> + if (addr <= ghcb && ghcb < addr + size) {
> skipped_addr = true;
> break;
> }
> @@ -1131,8 +1132,8 @@ static void shutdown_all_aps(void)
> void snp_kexec_finish(void)
> {
> struct sev_es_runtime_data *data;
> + unsigned long size, addr;
> unsigned int level, cpu;
> - unsigned long size;
> struct ghcb *ghcb;
> pte_t *pte;
>
> @@ -1160,8 +1161,10 @@ void snp_kexec_finish(void)
> ghcb = &data->ghcb_page;
> pte = lookup_address((unsigned long)ghcb, &level);
> size = page_level_size(level);
> - set_pte_enc(pte, level, (void *)ghcb);
> - snp_set_memory_private((unsigned long)ghcb, (size / PAGE_SIZE));
> + /* Handle the case of a huge page containing the GHCB page */
> + addr = (unsigned long)ghcb & page_level_mask(level);
> + set_pte_enc(pte, level, (void *)addr);
> + snp_set_memory_private(addr, (size / PAGE_SIZE));
> }
> }
>
