Messages in this thread Patches in this message |  | | Date | Sat, 3 Dec 2022 13:26:07 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v8 1/4] crypto: ccp - Name -1 return value as SEV_RET_NO_FW_CALL |
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On Fri, Nov 04, 2022 at 11:00:37PM +0000, Dionna Glaze wrote: > From: Peter Gonda <pgonda@google.com> > > The PSP can return a "firmware error" code of -1 in circumstances where > the PSP is not actually called. To make this protocol unambiguous, we
Please use passive voice in your commit message: no "we" or "I", etc, and describe your changes in imperative mood.
> add a constant naming the return value. > > Cc: Thomas Lendacky <Thomas.Lendacky@amd.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Joerg Roedel <jroedel@suse.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Andy Lutomirsky <luto@kernel.org> > Cc: John Allen <john.allen@amd.com> > Cc: Herbert Xu <herbert@gondor.apana.org.au> > Cc: "David S. Miller" <davem@davemloft.net> > > Signed-off-by: Peter Gonda <pgonda@google.com> > Signed-off-by: Dionna Glaze <dionnaglaze@google.com> > --- > drivers/crypto/ccp/sev-dev.c | 2 +- > include/uapi/linux/psp-sev.h | 7 +++++++ > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c > index 06fc7156c04f..97eb3544ab36 100644 > --- a/drivers/crypto/ccp/sev-dev.c > +++ b/drivers/crypto/ccp/sev-dev.c > @@ -444,7 +444,7 @@ static int __sev_platform_init_locked(int *error) > { > struct psp_device *psp = psp_master; > struct sev_device *sev; > - int rc = 0, psp_ret = -1; > + int rc = 0, psp_ret = SEV_RET_NO_FW_CALL; > int (*init_function)(int *error); > > if (!psp || !psp->sev_data)
Ok, lemme chase down this flow here:
__sev_platform_init_locked() calls that automatic variable function pointer ->init_function which already looks funky. See the end of this mail for a diff removing it and making the code more readable.
The called function can be one of two and both get the pointer to psp_ret as its only argument.
1. __sev_init_ex_locked() calls __sev_do_cmd_locked() and passes down *psp_ret.
or
2. __sev_init_locked(). Ditto.
Now, __sev_do_cmd_locked() will overwrite psp_ret when sev_wait_cmd_ioc() fails. So far so good. In the case __sev_do_cmd_locked() succeeds, it'll put there something else:
if (psp_ret) *psp_ret = reg & PSP_CMDRESP_ERR_MASK; So no caller will ever see SEV_RET_NO_FW_CALL, as far as I can tell.
And looking further through the rest of the set, nothing tests SEV_RET_NO_FW_CALL - it only gets assigned.
So why are we even bothering with this?
You can hand in *psp_ret uninitialized and you'll get a value in all cases. Unless I'm missing an angle.
> diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h > index 91b4c63d5cbf..1ad7f0a7e328 100644 > --- a/include/uapi/linux/psp-sev.h > +++ b/include/uapi/linux/psp-sev.h > @@ -36,6 +36,13 @@ enum { > * SEV Firmware status code > */ > typedef enum { > + /* > + * This error code is not in the SEV spec but is added to convey that > + * there was an error that prevented the SEV Firmware from being called. > + * This is (u32)-1 since the firmware error code is represented as a > + * 32-bit integer. > + */ > + SEV_RET_NO_FW_CALL = 0xffffffff,
What's wrong with having -1 here?
> SEV_RET_SUCCESS = 0, > SEV_RET_INVALID_PLATFORM_STATE, > SEV_RET_INVALID_GUEST_STATE, > --
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c index 97eb3544ab36..8bc4209b338b 100644 --- a/drivers/crypto/ccp/sev-dev.c +++ b/drivers/crypto/ccp/sev-dev.c @@ -440,12 +440,20 @@ static int __sev_init_ex_locked(int *error) return __sev_do_cmd_locked(SEV_CMD_INIT_EX, &data, error); } +static inline int __sev_do_init_locked(int *psp_ret) +{ + if (sev_init_ex_buffer) + return __sev_init_ex_locked(psp_ret); + else + + return __sev_init_locked(psp_ret); +} + static int __sev_platform_init_locked(int *error) { struct psp_device *psp = psp_master; struct sev_device *sev; - int rc = 0, psp_ret = SEV_RET_NO_FW_CALL; - int (*init_function)(int *error); + int rc = 0, psp_ret; if (!psp || !psp->sev_data) return -ENODEV; @@ -456,15 +464,12 @@ static int __sev_platform_init_locked(int *error) return 0; if (sev_init_ex_buffer) { - init_function = __sev_init_ex_locked; rc = sev_read_init_ex_file(); if (rc) return rc; - } else { - init_function = __sev_init_locked; } - rc = init_function(&psp_ret); + rc = __sev_do_init_locked(&psp_ret); if (rc && psp_ret == SEV_RET_SECURE_DATA_INVALID) { /* * Initialization command returned an integrity check failure @@ -473,9 +478,12 @@ static int __sev_platform_init_locked(int *error) * initialization function should succeed by replacing the state * with a reset state. */ - dev_err(sev->dev, "SEV: retrying INIT command because of SECURE_DATA_INVALID error. Retrying once to reset PSP SEV state."); - rc = init_function(&psp_ret); + dev_err(sev->dev, +"SEV: retrying INIT command because of SECURE_DATA_INVALID error. Retrying once to reset PSP SEV state."); + + rc = __sev_do_init_locked(&psp_ret); } + if (error) *error = psp_ret; diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h index 1ad7f0a7e328..a9ed9e846cd2 100644 --- a/include/uapi/linux/psp-sev.h +++ b/include/uapi/linux/psp-sev.h @@ -42,7 +42,7 @@ typedef enum { * This is (u32)-1 since the firmware error code is represented as a * 32-bit integer. */ - SEV_RET_NO_FW_CALL = 0xffffffff, + SEV_RET_NO_FW_CALL = -1, SEV_RET_SUCCESS = 0, SEV_RET_INVALID_PLATFORM_STATE, SEV_RET_INVALID_GUEST_STATE, -- Regards/Gruss, Boris.
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