Le 03/04/2021 à 01:37, Sean Christopherson a écrit :
Copy vmalloc'd data to an internal buffer instead of rejecting outright so that callers can put SEV command buffers on the stack without running afoul of CONFIG_VMAP_STACK=y. Currently, the largest supported command takes a 68 byte buffer, i.e. pretty much every command can be put on the stack. Because sev_cmd_mutex is held for the entirety of a transaction, only a single bounce buffer is required. Use a flexible array for the buffer, sized to hold the largest known command. Alternatively, the buffer could be a union of all known command structs, but that would incur a higher maintenance cost due to the need to update the union for every command in addition to updating the existing sev_cmd_buffer_len(). Align the buffer to an 8-byte boundary, mimicking the alignment that would be provided by the compiler if any of the structs were embedded directly. Note, sizeof() correctly incorporates this alignment. Cc: Brijesh Singh <brijesh.si...@amd.com> Cc: Borislav Petkov <b...@suse.de> Cc: Tom Lendacky <thomas.lenda...@amd.com> Signed-off-by: Sean Christopherson <sea...@google.com> --- drivers/crypto/ccp/sev-dev.c | 33 +++++++++++++++++++++++++++------ drivers/crypto/ccp/sev-dev.h | 7 +++++++ 2 files changed, 34 insertions(+), 6 deletions(-) diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c index 4c513318f16a..6d5882290cfc 100644 --- a/drivers/crypto/ccp/sev-dev.c +++ b/drivers/crypto/ccp/sev-dev.c @@ -135,13 +135,14 @@ static int sev_cmd_buffer_len(int cmd) return 0; }-static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)+static int __sev_do_cmd_locked(int cmd, void *__data, int *psp_ret) { struct psp_device *psp = psp_master; struct sev_device *sev; unsigned int phys_lsb, phys_msb; unsigned int reg, ret = 0; int buf_len; + void *data;if (!psp || !psp->sev_data)return -ENODEV; @@ -152,11 +153,21 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) sev = psp->sev_data;buf_len = sev_cmd_buffer_len(cmd);- if (WARN_ON_ONCE(!!data != !!buf_len)) + if (WARN_ON_ONCE(!!__data != !!buf_len)) return -EINVAL;- if (WARN_ON_ONCE(data && is_vmalloc_addr(data)))- return -EINVAL; + if (__data && is_vmalloc_addr(__data)) { + /* + * If the incoming buffer is virtually allocated, copy it to + * the driver's scratch buffer as __pa() will not work for such + * addresses, vmalloc_to_page() is not guaranteed to succeed, + * and vmalloc'd data may not be physically contiguous. + */ + data = sev->cmd_buf; + memcpy(data, __data, buf_len); + } else { + data = __data; + }
I don't know how big commands are, but if they are small, it would probably be more efficient to inconditionnally copy them to the buffer rather then doing the test.
/* Get the physical address of the command buffer */phys_lsb = data ? lower_32_bits(__psp_pa(data)) : 0; @@ -204,6 +215,13 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret) print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data, buf_len, false);+ /*+ * Copy potential output from the PSP back to __data. Do this even on + * failure in case the caller wants to glean something from the error. + */ + if (__data && data != __data) + memcpy(__data, data, buf_len); + return ret; }@@ -978,9 +996,12 @@ int sev_dev_init(struct psp_device *psp){ struct device *dev = psp->dev; struct sev_device *sev; - int ret = -ENOMEM; + int ret = -ENOMEM, cmd_buf_size = 0, i;- sev = devm_kzalloc(dev, sizeof(*sev), GFP_KERNEL);+ for (i = 0; i < SEV_CMD_MAX; i++) + cmd_buf_size = max(cmd_buf_size, sev_cmd_buffer_len(i)); + + sev = devm_kzalloc(dev, sizeof(*sev) + cmd_buf_size, GFP_KERNEL); if (!sev) goto e_err;diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.hindex dd5c4fe82914..b43283ce2d73 100644 --- a/drivers/crypto/ccp/sev-dev.h +++ b/drivers/crypto/ccp/sev-dev.h @@ -52,6 +52,13 @@ struct sev_device { u8 api_major; u8 api_minor; u8 build; + + /* + * Buffer used for incoming commands whose physical address cannot be + * resolved via __pa(), e.g. stack pointers when CONFIG_VMAP_STACK=y. + * Note, alignment isn't strictly required. + */ + u8 cmd_buf[] __aligned(8); };int sev_dev_init(struct psp_device *psp);
