Hi Alexey,
On 6/17/25 4:43 AM, Alexey Kardashevskiy wrote:
> The __snp_alloc_firmware_pages() helper allocates pages in the firmware
> state (alloc + rmpupdate). In case of failed rmpupdate, it tries
> reclaiming pages with already changed state. This requires calling
> the PSP firmware and since there is sev_cmd_mutex to guard such calls,
> the helper takes a "locked" parameter so specify if the lock needs to
> be held.
>
> Most calls happen from snp_alloc_firmware_page() which executes without
> the lock. However
>
> commit 24512afa4336 ("crypto: ccp: Handle the legacy TMR allocation when SNP is enabled")
>
> switched sev_fw_alloc() from alloc_pages() (which does not call the PSP) to
> __snp_alloc_firmware_pages() (which does) but did not account for the fact
> that sev_fw_alloc() is called from __sev_platform_init_locked()
> (via __sev_platform_init_handle_tmr()) and executes with the lock held.
>
> Add a "locked" parameter to __snp_alloc_firmware_pages().
> Make sev_fw_alloc() use the new parameter to prevent potential deadlock in
> rmp_mark_pages_firmware() if rmpupdate() failed.
>
> Fixes: 24512afa4336 ("crypto: ccp: Handle the legacy TMR allocation when SNP is enabled")
> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxx>
Thank you for fixing this.
I was facing a locking issue and was writing a similar patch when I
discovered this!
Reviewed-by: Pratik R. Sampat <prsampat@xxxxxxx>
> ---
> drivers/crypto/ccp/sev-dev.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 3451bada884e..16a11d5efe46 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -434,7 +434,7 @@ static int rmp_mark_pages_firmware(unsigned long paddr, unsigned int npages, boo
> return rc;
> }
>
> -static struct page *__snp_alloc_firmware_pages(gfp_t gfp_mask, int order)
> +static struct page *__snp_alloc_firmware_pages(gfp_t gfp_mask, int order, bool locked)
> {
> unsigned long npages = 1ul << order, paddr;
> struct sev_device *sev;
> @@ -453,7 +453,7 @@ static struct page *__snp_alloc_firmware_pages(gfp_t gfp_mask, int order)
> return page;
>
> paddr = __pa((unsigned long)page_address(page));
> - if (rmp_mark_pages_firmware(paddr, npages, false))
> + if (rmp_mark_pages_firmware(paddr, npages, locked))
> return NULL;
>
> return page;
> @@ -463,7 +463,7 @@ void *snp_alloc_firmware_page(gfp_t gfp_mask)
> {
> struct page *page;
>
> - page = __snp_alloc_firmware_pages(gfp_mask, 0);
> + page = __snp_alloc_firmware_pages(gfp_mask, 0, false);
>
> return page ? page_address(page) : NULL;
> }
> @@ -498,7 +498,7 @@ static void *sev_fw_alloc(unsigned long len)
> {
> struct page *page;
>
> - page = __snp_alloc_firmware_pages(GFP_KERNEL, get_order(len));
> + page = __snp_alloc_firmware_pages(GFP_KERNEL, get_order(len), true);
> if (!page)
> return NULL;
>
