On Thu, Dec 24, 2015 at 12:30:26PM +0300, Andrey Smetanin wrote:
> Currently on x86 arch we has already 32 requests defined
> so the newer request bits can't be placed inside
> vcpu->requests(unsigned long) inside x86 32 bit system.
> But we are going to add a new request in x86 arch
> for Hyper-V tsc page support.
>
> To solve the problem the patch replaces vcpu->requests by
> bitmap with 64 bit length and uses bitmap API.
>
> The patch consists of:
> * announce kvm_vcpu_has_requests() to check whether vcpu has
> requests
> * announce kvm_vcpu_requests() to get vcpu requests pointer
I think that if abstracting out the implementation of the request
container is what you're after, you'd better not define this function;
accesses to the request map should be through your accessor functions.
> * announce kvm_clear_request() to clear particular vcpu request
> * replace if (vcpu->requests) by if (kvm_vcpu_has_requests(vcpu))
> * replace clear_bit(req, vcpu->requests) by
> kvm_clear_request(req, vcpu)
Apparently one accessor is missing: test the presence of a request
without clearing it from the bitmap (because kvm_check_request() clears
it).
> diff --git a/arch/powerpc/kvm/trace.h b/arch/powerpc/kvm/trace.h
> index 2e0e67e..4015b88 100644
> --- a/arch/powerpc/kvm/trace.h
> +++ b/arch/powerpc/kvm/trace.h
> @@ -109,7 +109,7 @@ TRACE_EVENT(kvm_check_requests,
>
> TP_fast_assign(
> __entry->cpu_nr = vcpu->vcpu_id;
> - __entry->requests = vcpu->requests;
> + __entry->requests = (__u32)kvm_vcpu_requests(vcpu)[0];
> ),
This doesn't make sense, to expose only subset of the requests. BTW I
don't see this event in Linus tree, nor in linux-next, so I'm not quite
sure why it's formed this way; I guess the interesting part is the
request number and the return value (i.e. whether it's set), not the
whole bitmap.
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5957,7 +5957,7 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
> if (intr_window_requested && vmx_interrupt_allowed(vcpu))
> return handle_interrupt_window(&vmx->vcpu);
>
> - if (test_bit(KVM_REQ_EVENT, &vcpu->requests))
> + if (test_bit(KVM_REQ_EVENT, kvm_vcpu_requests(vcpu)))
Here you'd rather want that function to test for the request without
clearing it.
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2117,7 +2117,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>
> if (ka->boot_vcpu_runs_old_kvmclock != tmp)
> set_bit(KVM_REQ_MASTERCLOCK_UPDATE,
> - &vcpu->requests);
> + kvm_vcpu_requests(vcpu));
This should have been kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
> @@ -8048,7 +8048,7 @@ static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
> if (atomic_read(&vcpu->arch.nmi_queued))
> return true;
>
> - if (test_bit(KVM_REQ_SMI, &vcpu->requests))
> + if (test_bit(KVM_REQ_SMI, kvm_vcpu_requests(vcpu)))
Again the test-only accessor is due here.
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -146,6 +146,8 @@ static inline bool is_error_page(struct page *page)
> #define KVM_REQ_HV_EXIT 30
> #define KVM_REQ_HV_STIMER 31
>
> +#define KVM_REQ_MAX 64
> +
> #define KVM_USERSPACE_IRQ_SOURCE_ID 0
> #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID 1
>
> @@ -233,7 +235,7 @@ struct kvm_vcpu {
> int vcpu_id;
> int srcu_idx;
> int mode;
> - unsigned long requests;
> + DECLARE_BITMAP(requests, KVM_REQ_MAX);
> unsigned long guest_debug;
>
> int pre_pcpu;
> @@ -286,6 +288,16 @@ struct kvm_vcpu {
> struct kvm_vcpu_arch arch;
> };
>
> +static inline bool kvm_vcpu_has_requests(struct kvm_vcpu *vcpu)
> +{
> + return !bitmap_empty(vcpu->requests, KVM_REQ_MAX);
> +}
> +
> +static inline ulong *kvm_vcpu_requests(struct kvm_vcpu *vcpu)
> +{
> + return (ulong *)vcpu->requests;
> +}
As I wrote above, I believe this function doesn't belong in the API.
> +
> static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu)
> {
> return cmpxchg(&vcpu->mode, IN_GUEST_MODE, EXITING_GUEST_MODE);
> @@ -1002,7 +1014,7 @@ static inline bool kvm_is_error_gpa(struct kvm *kvm, gpa_t gpa)
>
> static inline void kvm_migrate_timers(struct kvm_vcpu *vcpu)
> {
> - set_bit(KVM_REQ_MIGRATE_TIMER, &vcpu->requests);
> + set_bit(KVM_REQ_MIGRATE_TIMER, kvm_vcpu_requests(vcpu));
kvm_make_request(KVM_REQ_MIGRATE_TIMER, vcpu);
> @@ -1118,19 +1130,24 @@ static inline bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu) { return true; }
>
> static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu)
> {
> - set_bit(req, &vcpu->requests);
> + set_bit(req, kvm_vcpu_requests(vcpu));
> }
>
> static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
> {
> - if (test_bit(req, &vcpu->requests)) {
> - clear_bit(req, &vcpu->requests);
> + if (test_bit(req, kvm_vcpu_requests(vcpu))) {
> + clear_bit(req, kvm_vcpu_requests(vcpu));
> return true;
> } else {
> return false;
> }
I wonder why this doesn't use test_and_clear_bit instead.
Roman.
