Messages in this thread | | | Subject | Re: [PATCH 3/5] crypto: ccp: Play nice with vmalloc'd memory for SEV command structs | From | Christophe Leroy <> | Date | Sat, 3 Apr 2021 19:13:42 +0200 |
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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.singh@amd.com> > Cc: Borislav Petkov <bp@suse.de> > Cc: Tom Lendacky <thomas.lendacky@amd.com> > Signed-off-by: Sean Christopherson <seanjc@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))
Why do you need a double !! ? I think !__data != !buf_len should be enough.
> 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; > + } > > /* 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)
IIUC, when __data is NULL, data is also NULL, so this double test is useless.
Checking data != __data should be enough
> + 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.h > index 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); >
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