| Message ID | 20210816150718.3063877-3-scgl@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: s390: Some gaccess cleanup | expand |
On Mon, 16 Aug 2021 17:07:17 +0200 Janis Schoetterl-Glausch <scgl@linux.ibm.com> wrote: > Do not round down the first address to the page boundary, just translate > it normally, which gives the value we care about in the first place. > Given this, translating a single address is just the special case of > translating a range spanning a single page. > > Make the output optional, so the function can be used to just check a > range. I like the idea, but see a few nits below > > Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com> > --- > arch/s390/kvm/gaccess.c | 91 ++++++++++++++++++----------------------- > 1 file changed, 39 insertions(+), 52 deletions(-) > > diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c > index df83de0843de..e5a19d8b30e2 100644 > --- a/arch/s390/kvm/gaccess.c > +++ b/arch/s390/kvm/gaccess.c > @@ -794,35 +794,45 @@ static int low_address_protection_enabled(struct kvm_vcpu *vcpu, > return 1; > } > > -static int guest_page_range(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, > - unsigned long *pages, unsigned long nr_pages, > - const union asce asce, enum gacc_mode mode) > +/* Stores the gpas for each page in a real/virtual range into @gpas > + * Modifies the 'struct kvm_s390_pgm_info pgm' member of @vcpu in the same > + * way read_guest/write_guest do, the meaning of the return value is likewise this comment is a bit confusing; why telling us to look what a different function is doing? either don't mention this at all (since it's more or less the expected behaviour), or explain in full what's going on > + * the same. > + * If @gpas is NULL only the checks are performed. > + */ > +static int guest_range_to_gpas(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, > + unsigned long *gpas, unsigned long len, > + const union asce asce, enum gacc_mode mode) > { > psw_t *psw = &vcpu->arch.sie_block->gpsw; > + unsigned long gpa; > + unsigned int seg; > + unsigned int offset = offset_in_page(ga); > int lap_enabled, rc = 0; > enum prot_type prot; > > lap_enabled = low_address_protection_enabled(vcpu, asce); > - while (nr_pages) { > + while ((seg = min(PAGE_SIZE - offset, len)) != 0) { I'm not terribly fond of assignments-as-values; moreover offset is used only once. why not something like: seg = min(PAGE_SIZE - offset, len); while (seg) { ... seg = min(PAGE_SIZE, len); } or maybe even: seg = min(PAGE_SIZE - offset, len); for (; seg; seg = min(PAGE_SIZE, len)) { (although the one with the while is perhaps more readable) > ga = kvm_s390_logical_to_effective(vcpu, ga); > if (mode == GACC_STORE && lap_enabled && is_low_address(ga)) > return trans_exc(vcpu, PGM_PROTECTION, ga, ar, mode, > PROT_TYPE_LA); > - ga &= PAGE_MASK; > if (psw_bits(*psw).dat) { > - rc = guest_translate(vcpu, ga, pages, asce, mode, &prot); > + rc = guest_translate(vcpu, ga, &gpa, asce, mode, &prot); > if (rc < 0) > return rc; > } else { > - *pages = kvm_s390_real_to_abs(vcpu, ga); > - if (kvm_is_error_gpa(vcpu->kvm, *pages)) > + gpa = kvm_s390_real_to_abs(vcpu, ga); > + if (kvm_is_error_gpa(vcpu->kvm, gpa)) > rc = PGM_ADDRESSING; > } > if (rc) > return trans_exc(vcpu, rc, ga, ar, mode, prot); > - ga += PAGE_SIZE; > - pages++; > - nr_pages--; > + if (gpas) > + *gpas++ = gpa; > + offset = 0; > + ga += seg; > + len -= seg; > } > return 0; > } > @@ -845,10 +855,10 @@ int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data, > unsigned long len, enum gacc_mode mode) > { > psw_t *psw = &vcpu->arch.sie_block->gpsw; > - unsigned long nr_pages, gpa, idx; > + unsigned long nr_pages, idx; > unsigned int seg; > - unsigned long pages_array[2]; > - unsigned long *pages; > + unsigned long gpa_array[2]; > + unsigned long *gpas; reverse Christmas tree? also, since you're touching this: have you checked if a different size for the array would bring any benefit? 2 seems a little too small, but I have no idea if anything bigger would bring any advantages. > int need_ipte_lock; > union asce asce; > int rc; > @@ -860,27 +870,25 @@ int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data, > if (rc) > return rc; > nr_pages = (((ga & ~PAGE_MASK) + len - 1) >> PAGE_SHIFT) + 1; > - pages = pages_array; > - if (nr_pages > ARRAY_SIZE(pages_array)) > - pages = vmalloc(array_size(nr_pages, sizeof(unsigned long))); > - if (!pages) > + gpas = gpa_array; > + if (nr_pages > ARRAY_SIZE(gpa_array)) > + gpas = vmalloc(array_size(nr_pages, sizeof(unsigned long))); > + if (!gpas) > return -ENOMEM; > need_ipte_lock = psw_bits(*psw).dat && !asce.r; > if (need_ipte_lock) > ipte_lock(vcpu); > - rc = guest_page_range(vcpu, ga, ar, pages, nr_pages, asce, mode); > + rc = guest_range_to_gpas(vcpu, ga, ar, gpas, len, asce, mode); > for (idx = 0; idx < nr_pages && !rc; idx++) { > - gpa = pages[idx] + offset_in_page(ga); > - seg = min(PAGE_SIZE - offset_in_page(gpa), len); > - rc = access_guest_frame(vcpu->kvm, mode, gpa, data, seg); > + seg = min(PAGE_SIZE - offset_in_page(gpas[idx]), len); > + rc = access_guest_frame(vcpu->kvm, mode, gpas[idx], data, seg); > len -= seg; > - ga += seg; > data += seg; > } > if (need_ipte_lock) > ipte_unlock(vcpu); > - if (nr_pages > ARRAY_SIZE(pages_array)) > - vfree(pages); > + if (nr_pages > ARRAY_SIZE(gpa_array)) > + vfree(gpas); > return rc; > } > > @@ -914,8 +922,6 @@ int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra, > int guest_translate_address(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, > unsigned long *gpa, enum gacc_mode mode) > { > - psw_t *psw = &vcpu->arch.sie_block->gpsw; > - enum prot_type prot; > union asce asce; > int rc; > > @@ -923,23 +929,7 @@ int guest_translate_address(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, > rc = get_vcpu_asce(vcpu, &asce, gva, ar, mode); > if (rc) > return rc; > - if (is_low_address(gva) && low_address_protection_enabled(vcpu, asce)) { > - if (mode == GACC_STORE) > - return trans_exc(vcpu, PGM_PROTECTION, gva, 0, > - mode, PROT_TYPE_LA); > - } > - > - if (psw_bits(*psw).dat && !asce.r) { /* Use DAT? */ > - rc = guest_translate(vcpu, gva, gpa, asce, mode, &prot); > - if (rc > 0) > - return trans_exc(vcpu, rc, gva, 0, mode, prot); > - } else { > - *gpa = kvm_s390_real_to_abs(vcpu, gva); > - if (kvm_is_error_gpa(vcpu->kvm, *gpa)) > - return trans_exc(vcpu, rc, gva, PGM_ADDRESSING, mode, 0); > - } > - > - return rc; > + return guest_range_to_gpas(vcpu, gva, ar, gpa, 1, asce, mode); > } > > /** > @@ -948,17 +938,14 @@ int guest_translate_address(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, > int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, > unsigned long length, enum gacc_mode mode) > { > - unsigned long gpa; > - unsigned long currlen; > + union asce asce; > int rc = 0; > > + rc = get_vcpu_asce(vcpu, &asce, gva, ar, mode); > + if (rc) > + return rc; > ipte_lock(vcpu); > - while (length > 0 && !rc) { > - currlen = min(length, PAGE_SIZE - (gva % PAGE_SIZE)); > - rc = guest_translate_address(vcpu, gva, ar, &gpa, mode); > - gva += currlen; > - length -= currlen; > - } > + rc = guest_range_to_gpas(vcpu, gva, ar, NULL, length, asce, mode); > ipte_unlock(vcpu); > > return rc;
On 8/18/21 12:08 PM, Claudio Imbrenda wrote: > On Mon, 16 Aug 2021 17:07:17 +0200 > Janis Schoetterl-Glausch <scgl@linux.ibm.com> wrote: > >> Do not round down the first address to the page boundary, just translate >> it normally, which gives the value we care about in the first place. >> Given this, translating a single address is just the special case of >> translating a range spanning a single page. >> >> Make the output optional, so the function can be used to just check a >> range. > > I like the idea, but see a few nits below > >> >> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com> >> --- >> arch/s390/kvm/gaccess.c | 91 ++++++++++++++++++----------------------- >> 1 file changed, 39 insertions(+), 52 deletions(-) >> >> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c >> index df83de0843de..e5a19d8b30e2 100644 >> --- a/arch/s390/kvm/gaccess.c >> +++ b/arch/s390/kvm/gaccess.c >> @@ -794,35 +794,45 @@ static int low_address_protection_enabled(struct kvm_vcpu *vcpu, >> return 1; >> } >> >> -static int guest_page_range(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, >> - unsigned long *pages, unsigned long nr_pages, >> - const union asce asce, enum gacc_mode mode) >> +/* Stores the gpas for each page in a real/virtual range into @gpas >> + * Modifies the 'struct kvm_s390_pgm_info pgm' member of @vcpu in the same >> + * way read_guest/write_guest do, the meaning of the return value is likewise > > this comment is a bit confusing; why telling us to look what a > different function is doing? > > either don't mention this at all (since it's more or less the expected > behaviour), or explain in full what's going on Yeah, it's not ideal. I haven't decided yet what I'll do. I think a comment would be helpful, and it may be expected behavior only if one has looked at the code for long enough :). > >> + * the same. >> + * If @gpas is NULL only the checks are performed. >> + */ >> +static int guest_range_to_gpas(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, >> + unsigned long *gpas, unsigned long len, >> + const union asce asce, enum gacc_mode mode) >> { >> psw_t *psw = &vcpu->arch.sie_block->gpsw; >> + unsigned long gpa; >> + unsigned int seg; >> + unsigned int offset = offset_in_page(ga); >> int lap_enabled, rc = 0; >> enum prot_type prot; >> >> lap_enabled = low_address_protection_enabled(vcpu, asce); >> - while (nr_pages) { >> + while ((seg = min(PAGE_SIZE - offset, len)) != 0) { > > I'm not terribly fond of assignments-as-values; moreover offset is used > only once. > > why not something like: > > seg = min(PAGE_SIZE - offset, len); > while (seg) { > > ... > > seg = min(PAGE_SIZE, len); > } > > or maybe even: > > seg = min(PAGE_SIZE - offset, len); > for (; seg; seg = min(PAGE_SIZE, len)) { > > (although the one with the while is perhaps more readable) That code pattern is not entirely uncommon, but I'll change it to: while(min(PAGE_SIZE - offset, len) > 0) { seg = min(PAGE_SIZE - offset, len); ... } which I think reads better than having the assignment at the end. I assume the compiler gets rid of the redundancy. > [...] >> @@ -845,10 +855,10 @@ int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data, >> unsigned long len, enum gacc_mode mode) >> { >> psw_t *psw = &vcpu->arch.sie_block->gpsw; >> - unsigned long nr_pages, gpa, idx; >> + unsigned long nr_pages, idx; >> unsigned int seg; >> - unsigned long pages_array[2]; >> - unsigned long *pages; >> + unsigned long gpa_array[2]; >> + unsigned long *gpas; > > reverse Christmas tree? > > also, since you're touching this: have you checked if a different size > for the array would bring any benefit? > 2 seems a little too small, but I have no idea if anything bigger would > bring any advantages. I have not checked it, no. When emulating instructions, you would only need >2 entries if an operand is >8k or >4k and weirdly aligned, hardly seems like a common occurrence. On the other hand, bumping it up should not have any negative consequences. I'll leave it as is. [...]
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c index df83de0843de..e5a19d8b30e2 100644 --- a/arch/s390/kvm/gaccess.c +++ b/arch/s390/kvm/gaccess.c @@ -794,35 +794,45 @@ static int low_address_protection_enabled(struct kvm_vcpu *vcpu, return 1; } -static int guest_page_range(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, - unsigned long *pages, unsigned long nr_pages, - const union asce asce, enum gacc_mode mode) +/* Stores the gpas for each page in a real/virtual range into @gpas + * Modifies the 'struct kvm_s390_pgm_info pgm' member of @vcpu in the same + * way read_guest/write_guest do, the meaning of the return value is likewise + * the same. + * If @gpas is NULL only the checks are performed. + */ +static int guest_range_to_gpas(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, + unsigned long *gpas, unsigned long len, + const union asce asce, enum gacc_mode mode) { psw_t *psw = &vcpu->arch.sie_block->gpsw; + unsigned long gpa; + unsigned int seg; + unsigned int offset = offset_in_page(ga); int lap_enabled, rc = 0; enum prot_type prot; lap_enabled = low_address_protection_enabled(vcpu, asce); - while (nr_pages) { + while ((seg = min(PAGE_SIZE - offset, len)) != 0) { ga = kvm_s390_logical_to_effective(vcpu, ga); if (mode == GACC_STORE && lap_enabled && is_low_address(ga)) return trans_exc(vcpu, PGM_PROTECTION, ga, ar, mode, PROT_TYPE_LA); - ga &= PAGE_MASK; if (psw_bits(*psw).dat) { - rc = guest_translate(vcpu, ga, pages, asce, mode, &prot); + rc = guest_translate(vcpu, ga, &gpa, asce, mode, &prot); if (rc < 0) return rc; } else { - *pages = kvm_s390_real_to_abs(vcpu, ga); - if (kvm_is_error_gpa(vcpu->kvm, *pages)) + gpa = kvm_s390_real_to_abs(vcpu, ga); + if (kvm_is_error_gpa(vcpu->kvm, gpa)) rc = PGM_ADDRESSING; } if (rc) return trans_exc(vcpu, rc, ga, ar, mode, prot); - ga += PAGE_SIZE; - pages++; - nr_pages--; + if (gpas) + *gpas++ = gpa; + offset = 0; + ga += seg; + len -= seg; } return 0; } @@ -845,10 +855,10 @@ int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data, unsigned long len, enum gacc_mode mode) { psw_t *psw = &vcpu->arch.sie_block->gpsw; - unsigned long nr_pages, gpa, idx; + unsigned long nr_pages, idx; unsigned int seg; - unsigned long pages_array[2]; - unsigned long *pages; + unsigned long gpa_array[2]; + unsigned long *gpas; int need_ipte_lock; union asce asce; int rc; @@ -860,27 +870,25 @@ int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data, if (rc) return rc; nr_pages = (((ga & ~PAGE_MASK) + len - 1) >> PAGE_SHIFT) + 1; - pages = pages_array; - if (nr_pages > ARRAY_SIZE(pages_array)) - pages = vmalloc(array_size(nr_pages, sizeof(unsigned long))); - if (!pages) + gpas = gpa_array; + if (nr_pages > ARRAY_SIZE(gpa_array)) + gpas = vmalloc(array_size(nr_pages, sizeof(unsigned long))); + if (!gpas) return -ENOMEM; need_ipte_lock = psw_bits(*psw).dat && !asce.r; if (need_ipte_lock) ipte_lock(vcpu); - rc = guest_page_range(vcpu, ga, ar, pages, nr_pages, asce, mode); + rc = guest_range_to_gpas(vcpu, ga, ar, gpas, len, asce, mode); for (idx = 0; idx < nr_pages && !rc; idx++) { - gpa = pages[idx] + offset_in_page(ga); - seg = min(PAGE_SIZE - offset_in_page(gpa), len); - rc = access_guest_frame(vcpu->kvm, mode, gpa, data, seg); + seg = min(PAGE_SIZE - offset_in_page(gpas[idx]), len); + rc = access_guest_frame(vcpu->kvm, mode, gpas[idx], data, seg); len -= seg; - ga += seg; data += seg; } if (need_ipte_lock) ipte_unlock(vcpu); - if (nr_pages > ARRAY_SIZE(pages_array)) - vfree(pages); + if (nr_pages > ARRAY_SIZE(gpa_array)) + vfree(gpas); return rc; } @@ -914,8 +922,6 @@ int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra, int guest_translate_address(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, unsigned long *gpa, enum gacc_mode mode) { - psw_t *psw = &vcpu->arch.sie_block->gpsw; - enum prot_type prot; union asce asce; int rc; @@ -923,23 +929,7 @@ int guest_translate_address(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, rc = get_vcpu_asce(vcpu, &asce, gva, ar, mode); if (rc) return rc; - if (is_low_address(gva) && low_address_protection_enabled(vcpu, asce)) { - if (mode == GACC_STORE) - return trans_exc(vcpu, PGM_PROTECTION, gva, 0, - mode, PROT_TYPE_LA); - } - - if (psw_bits(*psw).dat && !asce.r) { /* Use DAT? */ - rc = guest_translate(vcpu, gva, gpa, asce, mode, &prot); - if (rc > 0) - return trans_exc(vcpu, rc, gva, 0, mode, prot); - } else { - *gpa = kvm_s390_real_to_abs(vcpu, gva); - if (kvm_is_error_gpa(vcpu->kvm, *gpa)) - return trans_exc(vcpu, rc, gva, PGM_ADDRESSING, mode, 0); - } - - return rc; + return guest_range_to_gpas(vcpu, gva, ar, gpa, 1, asce, mode); } /** @@ -948,17 +938,14 @@ int guest_translate_address(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, unsigned long length, enum gacc_mode mode) { - unsigned long gpa; - unsigned long currlen; + union asce asce; int rc = 0; + rc = get_vcpu_asce(vcpu, &asce, gva, ar, mode); + if (rc) + return rc; ipte_lock(vcpu); - while (length > 0 && !rc) { - currlen = min(length, PAGE_SIZE - (gva % PAGE_SIZE)); - rc = guest_translate_address(vcpu, gva, ar, &gpa, mode); - gva += currlen; - length -= currlen; - } + rc = guest_range_to_gpas(vcpu, gva, ar, NULL, length, asce, mode); ipte_unlock(vcpu); return rc;
Do not round down the first address to the page boundary, just translate it normally, which gives the value we care about in the first place. Given this, translating a single address is just the special case of translating a range spanning a single page. Make the output optional, so the function can be used to just check a range. Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com> --- arch/s390/kvm/gaccess.c | 91 ++++++++++++++++++----------------------- 1 file changed, 39 insertions(+), 52 deletions(-)