Messages in this thread | | | Date | Tue, 18 Jan 2022 18:54:18 +0100 | Subject | Re: [PATCH v2 22/30] KVM: s390: intercept the rpcit instruction | From | Pierre Morel <> |
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On 1/18/22 18:27, Matthew Rosato wrote: > On 1/18/22 6:05 AM, Pierre Morel wrote: >> >> >> On 1/14/22 21:31, Matthew Rosato wrote: >>> For faster handling of PCI translation refreshes, intercept in KVM >>> and call the associated handler. >>> >>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com> >>> --- >>> arch/s390/kvm/priv.c | 46 ++++++++++++++++++++++++++++++++++++++++++++ >>> 1 file changed, 46 insertions(+) >>> >>> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c >>> index 417154b314a6..5b65c1830de2 100644 >>> --- a/arch/s390/kvm/priv.c >>> +++ b/arch/s390/kvm/priv.c >>> @@ -29,6 +29,7 @@ >>> #include <asm/ap.h> >>> #include "gaccess.h" >>> #include "kvm-s390.h" >>> +#include "pci.h" >>> #include "trace.h" >>> static int handle_ri(struct kvm_vcpu *vcpu) >>> @@ -335,6 +336,49 @@ static int handle_rrbe(struct kvm_vcpu *vcpu) >>> return 0; >>> } >>> +static int handle_rpcit(struct kvm_vcpu *vcpu) >>> +{ >>> + int reg1, reg2; >>> + u8 status; >>> + int rc; >>> + >>> + if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE) >>> + return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP); >>> + >>> + /* If the host doesn't support PCI, it must be an emulated >>> device */ >>> + if (!IS_ENABLED(CONFIG_PCI)) >>> + return -EOPNOTSUPP; >> >> AFAIU this makes also sure that the following code is not compiled in >> case PCI is not supported. >> >> I am not very used to compilation options, is it true with all our >> compilers and options? >> Or do we have to specify a compiler version? >> >> Another concern is, shouldn't we use IS_ENABLED(CONFIG_VFIO_PCI) ? > > Same idea as in the other thread -- What we are trying to protect > against here is referencing symbols that won't be linked (like > zpci_refresh_trans, or the aift->mdd a few lines below) > > It is indeed true that we should never need to handle the rpcit > intercept in KVM if CONFIG_VFIO_PCI=n -- but the necessary symbols/code > are linked at least, so we can just let the SHM logic sort this out. > When CONFIG_PCI=y|m, arch/s390/kvm/pci.o will be linked and so we can > compare the function handle against afit->mdd (check to see if the > device is emulated) and use this to determine whether or not to > immediately send to userspace -- And if CONFIG_VFIO_PCI=n, a SHM bit > will always be on and so we'll always go to userspace via this check.
So we agree. But as I I said somewhere else I wonder if CONFIG_VFIO_PCI_ZDEV would not even be better here.
> >> >> >> >>> + >>> + kvm_s390_get_regs_rre(vcpu, ®1, ®2); >>> + >>> + /* If the device has a SHM bit on, let userspace take care of >>> this */ >>> + if (((vcpu->run->s.regs.gprs[reg1] >> 32) & aift->mdd) != 0) >>> + return -EOPNOTSUPP; >>> + >>> + rc = kvm_s390_pci_refresh_trans(vcpu, vcpu->run->s.regs.gprs[reg1], >>> + vcpu->run->s.regs.gprs[reg2], >>> + vcpu->run->s.regs.gprs[reg2+1], >>> + &status); >>> + >>> + switch (rc) { >>> + case 0: >>> + kvm_s390_set_psw_cc(vcpu, 0); >>> + break; >>> + case -EOPNOTSUPP: >>> + return -EOPNOTSUPP; >>> + default: >>> + vcpu->run->s.regs.gprs[reg1] &= 0xffffffff00ffffffUL; >>> + vcpu->run->s.regs.gprs[reg1] |= (u64) status << 24; >>> + if (status != 0) >>> + kvm_s390_set_psw_cc(vcpu, 1); >>> + else >>> + kvm_s390_set_psw_cc(vcpu, 3); >>> + break; >>> + } >>> + >>> + return 0; >>> +} >>> + >>> #define SSKE_NQ 0x8 >>> #define SSKE_MR 0x4 >>> #define SSKE_MC 0x2 >>> @@ -1275,6 +1319,8 @@ int kvm_s390_handle_b9(struct kvm_vcpu *vcpu) >>> return handle_essa(vcpu); >>> case 0xaf: >>> return handle_pfmf(vcpu); >>> + case 0xd3: >>> + return handle_rpcit(vcpu); >>> default: >>> return -EOPNOTSUPP; >>> } >>> >> >
-- Pierre Morel IBM Lab Boeblingen
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