On Mon, Jun 20, 2022 at 5:05 PM Ashish Kalra <Ashish.Kalra@xxxxxxx> wrote:
>
> From: Brijesh Singh <brijesh.singh@xxxxxxx>
>
> The behavior and requirement for the SEV-legacy command is altered when
> the SNP firmware is in the INIT state. See SEV-SNP firmware specification
> for more details.
>
> Allocate the Trusted Memory Region (TMR) as a 2mb sized/aligned region
> when SNP is enabled to satify new requirements for the SNP. Continue
satisfy
> allocating a 1mb region for !SNP configuration.
>
> While at it, provide API that can be used by others to allocate a page
> that can be used by the firmware. The immediate user for this API will
> be the KVM driver. The KVM driver to need to allocate a firmware context
> page during the guest creation. The context page need to be updated
> by the firmware. See the SEV-SNP specification for further details.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> ---
> drivers/crypto/ccp/sev-dev.c | 173 +++++++++++++++++++++++++++++++++--
> include/linux/psp-sev.h | 11 +++
> 2 files changed, 178 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 35d76333e120..0dbd99f29b25 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -79,6 +79,14 @@ static void *sev_es_tmr;
> #define NV_LENGTH (32 * 1024)
> static void *sev_init_ex_buffer;
>
> +/* When SEV-SNP is enabled the TMR needs to be 2MB aligned and 2MB size. */
> +#define SEV_SNP_ES_TMR_SIZE (2 * 1024 * 1024)
> +
> +static size_t sev_es_tmr_size = SEV_ES_TMR_SIZE;
Why not keep all this TMR stuff together near the SEV_ES_TMR_SIZE define?
> +
> +static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret);
> +static int sev_do_cmd(int cmd, void *data, int *psp_ret);
> +
> static inline bool sev_version_greater_or_equal(u8 maj, u8 min)
> {
> struct sev_device *sev = psp_master->sev_data;
> @@ -177,11 +185,161 @@ static int sev_cmd_buffer_len(int cmd)
> return 0;
> }
>
> +static void snp_leak_pages(unsigned long pfn, unsigned int npages)
> +{
> + WARN(1, "psc failed, pfn 0x%lx pages %d (leaking)\n", pfn, npages);
> + while (npages--) {
> + memory_failure(pfn, 0);
> + dump_rmpentry(pfn);
> + pfn++;
> + }
> +}
> +
> +static int snp_reclaim_pages(unsigned long pfn, unsigned int npages, bool locked)
> +{
> + struct sev_data_snp_page_reclaim data;
> + int ret, err, i, n = 0;
> +
> + for (i = 0; i < npages; i++) {
What about setting |n| here too, also the other increments.
for (i = 0, n = 0; i < npages; i++, n++, pfn++)
> + memset(&data, 0, sizeof(data));
> + data.paddr = pfn << PAGE_SHIFT;
> +
> + if (locked)
> + ret = __sev_do_cmd_locked(SEV_CMD_SNP_PAGE_RECLAIM, &data, &err);
> + else
> + ret = sev_do_cmd(SEV_CMD_SNP_PAGE_RECLAIM, &data, &err);
Can we change `sev_cmd_mutex` to some sort of nesting lock type? That
could clean up this if (locked) code.
> + if (ret)
> + goto cleanup;
> +
> + ret = rmp_make_shared(pfn, PG_LEVEL_4K);
> + if (ret)
> + goto cleanup;
> +
> + pfn++;
> + n++;
> + }
> +
> + return 0;
> +
> +cleanup:
> + /*
> + * If failed to reclaim the page then page is no longer safe to
> + * be released, leak it.
> + */
> + snp_leak_pages(pfn, npages - n);
> + return ret;
> +}
> +
> +static inline int rmp_make_firmware(unsigned long pfn, int level)
> +{
> + return rmp_make_private(pfn, 0, level, 0, true);
> +}
> +
> +static int snp_set_rmp_state(unsigned long paddr, unsigned int npages, bool to_fw, bool locked,
> + bool need_reclaim)
This function can do a lot and when I read the call sites its hard to
see what its doing since we have a combination of arguments which tell
us what behavior is happening, some of which are not valid (ex: to_fw
== true and need_reclaim == true is an invalid argument combination).
Also this for loop over |npages| is duplicated from
snp_reclaim_pages(). One improvement here is that on the current
snp_reclaim_pages() if we fail to reclaim a page we assume we cannot
reclaim the next pages, this may cause us to snp_leak_pages() more
pages than we actually need too.
What about something like this?
static snp_leak_page(u64 pfn, enum pg_level level)
{
memory_failure(pfn, 0);
dump_rmpentry(pfn);
}
static int snp_reclaim_page(u64 pfn, enum pg_level level)
{
int ret;
struct sev_data_snp_page_reclaim data;
ret = sev_do_cmd(SEV_CMD_SNP_PAGE_RECLAIM, &data, &err);
if (ret)
goto cleanup;
ret = rmp_make_shared(pfn, level);
if (ret)
goto cleanup;
return 0;
cleanup:
snp_leak_page(pfn, level)
}
typedef int (*rmp_state_change_func) (u64 pfn, enum pg_level level);
static int snp_set_rmp_state(unsigned long paddr, unsigned int npages,
rmp_state_change_func state_change, rmp_state_change_func cleanup)
{
struct sev_data_snp_page_reclaim data;
int ret, err, i, n = 0;
for (i = 0, n = 0; i < npages; i++, n++, pfn++) {
ret = state_change(pfn, PG_LEVEL_4K)
if (ret)
goto cleanup;
}
return 0;
cleanup:
for (; i>= 0; i--, n--, pfn--) {
cleanup(pfn, PG_LEVEL_4K);
}
return ret;
}
Then inside of __snp_alloc_firmware_pages():
snp_set_rmp_state(paddr, npages, rmp_make_firmware, snp_reclaim_page);
And inside of __snp_free_firmware_pages():
snp_set_rmp_state(paddr, npages, snp_reclaim_page, snp_leak_page);
Just a suggestion feel free to ignore. The readability comment could
be addressed much less invasively by just making separate functions
for each valid combination of arguments here. Like
snp_set_rmp_fw_state(), snp_set_rmp_shared_state(),
snp_set_rmp_release_state() or something.
> +{
> + unsigned long pfn = __sme_clr(paddr) >> PAGE_SHIFT; /* Cbit maybe set in the paddr */
> + int rc, n = 0, i;
> +
> + for (i = 0; i < npages; i++) {
> + if (to_fw)
> + rc = rmp_make_firmware(pfn, PG_LEVEL_4K);
> + else
> + rc = need_reclaim ? snp_reclaim_pages(pfn, 1, locked) :
> + rmp_make_shared(pfn, PG_LEVEL_4K);
> + if (rc)
> + goto cleanup;
> +
> + pfn++;
> + n++;
> + }
> +
> + return 0;
> +
> +cleanup:
> + /* Try unrolling the firmware state changes */
> + if (to_fw) {
> + /*
> + * Reclaim the pages which were already changed to the
> + * firmware state.
> + */
> + snp_reclaim_pages(paddr >> PAGE_SHIFT, n, locked);
> +
> + return rc;
> + }
> +
> + /*
> + * If failed to change the page state to shared, then its not safe
> + * to release the page back to the system, leak it.
> + */
> + snp_leak_pages(pfn, npages - n);
> +
> + return rc;
> +}
> +
> +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;
> + struct page *page;
> +
> + if (!psp_master || !psp_master->sev_data)
> + return NULL;
> +
> + page = alloc_pages(gfp_mask, order);
> + if (!page)
> + return NULL;
> +
> + /* If SEV-SNP is initialized then add the page in RMP table. */
> + sev = psp_master->sev_data;
> + if (!sev->snp_inited)
> + return page;
> +
> + paddr = __pa((unsigned long)page_address(page));
> + if (snp_set_rmp_state(paddr, npages, true, locked, false))
> + return NULL;
So what about the case where snp_set_rmp_state() fails but we were
able to reclaim all the pages? Should we be able to signal that to
callers so that we could free |page| here? But given this is an error
path already maybe we can optimize this in a follow up series.
> +
> + return page;
> +}
> +
> +void *snp_alloc_firmware_page(gfp_t gfp_mask)
> +{
> + struct page *page;
> +
> + page = __snp_alloc_firmware_pages(gfp_mask, 0, false);
> +
> + return page ? page_address(page) : NULL;
> +}
> +EXPORT_SYMBOL_GPL(snp_alloc_firmware_page);
> +
> +static void __snp_free_firmware_pages(struct page *page, int order, bool locked)
> +{
> + unsigned long paddr, npages = 1ul << order;
> +
> + if (!page)
> + return;
> +
> + paddr = __pa((unsigned long)page_address(page));
> + if (snp_set_rmp_state(paddr, npages, false, locked, true))
> + return;
Here we may be able to free some of |page| depending how where inside
of snp_set_rmp_state() we failed. But again given this is an error
path already maybe we can optimize this in a follow up series.
> +
> + __free_pages(page, order);
> +}
> +
> +void snp_free_firmware_page(void *addr)
> +{
> + if (!addr)
> + return;
> +
> + __snp_free_firmware_pages(virt_to_page(addr), 0, false);
> +}
> +EXPORT_SYMBOL(snp_free_firmware_page);
> +
> static void *sev_fw_alloc(unsigned long len)
> {
> struct page *page;
>
> - page = alloc_pages(GFP_KERNEL, get_order(len));
> + page = __snp_alloc_firmware_pages(GFP_KERNEL, get_order(len), false);
> if (!page)
> return NULL;
>
> @@ -393,7 +551,7 @@ static int __sev_init_locked(int *error)
> data.tmr_address = __pa(sev_es_tmr);
>
> data.flags |= SEV_INIT_FLAGS_SEV_ES;
> - data.tmr_len = SEV_ES_TMR_SIZE;
> + data.tmr_len = sev_es_tmr_size;
> }
>
> return __sev_do_cmd_locked(SEV_CMD_INIT, &data, error);
> @@ -421,7 +579,7 @@ static int __sev_init_ex_locked(int *error)
> data.tmr_address = __pa(sev_es_tmr);
>
> data.flags |= SEV_INIT_FLAGS_SEV_ES;
> - data.tmr_len = SEV_ES_TMR_SIZE;
> + data.tmr_len = sev_es_tmr_size;
> }
>
> return __sev_do_cmd_locked(SEV_CMD_INIT_EX, &data, error);
> @@ -818,6 +976,8 @@ static int __sev_snp_init_locked(int *error)
> sev->snp_inited = true;
> dev_dbg(sev->dev, "SEV-SNP firmware initialized\n");
>
> + sev_es_tmr_size = SEV_SNP_ES_TMR_SIZE;
> +
> return rc;
> }
>
> @@ -1341,8 +1501,9 @@ static void sev_firmware_shutdown(struct sev_device *sev)
> /* The TMR area was encrypted, flush it from the cache */
> wbinvd_on_all_cpus();
>
> - free_pages((unsigned long)sev_es_tmr,
> - get_order(SEV_ES_TMR_SIZE));
> + __snp_free_firmware_pages(virt_to_page(sev_es_tmr),
> + get_order(sev_es_tmr_size),
> + false);
> sev_es_tmr = NULL;
> }
>
> @@ -1430,7 +1591,7 @@ void sev_pci_init(void)
> }
>
> /* Obtain the TMR memory area for SEV-ES use */
> - sev_es_tmr = sev_fw_alloc(SEV_ES_TMR_SIZE);
> + sev_es_tmr = sev_fw_alloc(sev_es_tmr_size);
> if (!sev_es_tmr)
> dev_warn(sev->dev,
> "SEV: TMR allocation failed, SEV-ES support unavailable\n");
> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> index 9f921d221b75..a3bb792bb842 100644
> --- a/include/linux/psp-sev.h
> +++ b/include/linux/psp-sev.h
> @@ -12,6 +12,8 @@
> #ifndef __PSP_SEV_H__
> #define __PSP_SEV_H__
>
> +#include <linux/sev.h>
> +
> #include <uapi/linux/psp-sev.h>
>
> #ifdef CONFIG_X86
> @@ -940,6 +942,8 @@ int snp_guest_page_reclaim(struct sev_data_snp_page_reclaim *data, int *error);
> int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error);
>
> void *psp_copy_user_blob(u64 uaddr, u32 len);
> +void *snp_alloc_firmware_page(gfp_t mask);
> +void snp_free_firmware_page(void *addr);
>
> #else /* !CONFIG_CRYPTO_DEV_SP_PSP */
>
> @@ -981,6 +985,13 @@ static inline int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *erro
> return -ENODEV;
> }
>
> +static inline void *snp_alloc_firmware_page(gfp_t mask)
> +{
> + return NULL;
> +}
> +
> +static inline void snp_free_firmware_page(void *addr) { }
> +
> #endif /* CONFIG_CRYPTO_DEV_SP_PSP */
>
> #endif /* __PSP_SEV_H__ */
> --
> 2.25.1
>
