2022-04-22 09:43:04

by Anup Patel

Subject: [PATCH v2 5/7] RISC-V: KVM: Reduce KVM_MAX_VCPUS value

Currently, the KVM_MAX_VCPUS value is 16384 for RV64 and 128
for RV32.

The KVM_MAX_VCPUS value is too high for RV64 and too low for
RV32 compared to other architectures (e.g. x86 sets it to 1024
and ARM64 sets it to 512). The too high value of KVM_MAX_VCPUS
on RV64 also leads to VCPU mask on stack consuming 2KB.

We set KVM_MAX_VCPUS to 1024 for both RV64 and RV32 to be
aligned other architectures.

Signed-off-by: Anup Patel <[email protected]>
---
arch/riscv/include/asm/kvm_host.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 806f74dc0bfc..61d8b40e3d82 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -16,8 +16,7 @@
#include <asm/kvm_vcpu_fp.h>
#include <asm/kvm_vcpu_timer.h>

-#define KVM_MAX_VCPUS \
- ((HGATP_VMID_MASK >> HGATP_VMID_SHIFT) + 1)
+#define KVM_MAX_VCPUS 1024

#define KVM_HALT_POLL_NS_DEFAULT 500000

--
2.25.1

2022-05-04 19:13:06

by Atish Patra

Subject: Re: [PATCH v2 5/7] RISC-V: KVM: Reduce KVM_MAX_VCPUS value

On Wed, Apr 20, 2022 at 4:25 AM Anup Patel <[email protected]> wrote:
>
> Currently, the KVM_MAX_VCPUS value is 16384 for RV64 and 128
> for RV32.
>
> The KVM_MAX_VCPUS value is too high for RV64 and too low for
> RV32 compared to other architectures (e.g. x86 sets it to 1024
> and ARM64 sets it to 512). The too high value of KVM_MAX_VCPUS
> on RV64 also leads to VCPU mask on stack consuming 2KB.
>
> We set KVM_MAX_VCPUS to 1024 for both RV64 and RV32 to be
> aligned other architectures.
>
> Signed-off-by: Anup Patel <[email protected]>
> ---
> arch/riscv/include/asm/kvm_host.h | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index 806f74dc0bfc..61d8b40e3d82 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -16,8 +16,7 @@
> #include <asm/kvm_vcpu_fp.h>
> #include <asm/kvm_vcpu_timer.h>
>
> -#define KVM_MAX_VCPUS \
> - ((HGATP_VMID_MASK >> HGATP_VMID_SHIFT) + 1)
> +#define KVM_MAX_VCPUS 1024
>
> #define KVM_HALT_POLL_NS_DEFAULT 500000
>
> --
> 2.25.1
>

Reviewed-by: Atish Patra <[email protected]>

--
Regards,
Atish

2022-05-09 10:10:30

by Anup Patel

Subject: Re: [PATCH v2 5/7] RISC-V: KVM: Reduce KVM_MAX_VCPUS value

On Wed, May 4, 2022 at 7:45 AM Atish Patra <[email protected]> wrote:
>
> On Wed, Apr 20, 2022 at 4:25 AM Anup Patel <[email protected]> wrote:
> >
> > Currently, the KVM_MAX_VCPUS value is 16384 for RV64 and 128
> > for RV32.
> >
> > The KVM_MAX_VCPUS value is too high for RV64 and too low for
> > RV32 compared to other architectures (e.g. x86 sets it to 1024
> > and ARM64 sets it to 512). The too high value of KVM_MAX_VCPUS
> > on RV64 also leads to VCPU mask on stack consuming 2KB.
> >
> > We set KVM_MAX_VCPUS to 1024 for both RV64 and RV32 to be
> > aligned other architectures.
> >
> > Signed-off-by: Anup Patel <[email protected]>
> > ---
> > arch/riscv/include/asm/kvm_host.h | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> > index 806f74dc0bfc..61d8b40e3d82 100644
> > --- a/arch/riscv/include/asm/kvm_host.h
> > +++ b/arch/riscv/include/asm/kvm_host.h
> > @@ -16,8 +16,7 @@
> > #include <asm/kvm_vcpu_fp.h>
> > #include <asm/kvm_vcpu_timer.h>
> >
> > -#define KVM_MAX_VCPUS \
> > - ((HGATP_VMID_MASK >> HGATP_VMID_SHIFT) + 1)
> > +#define KVM_MAX_VCPUS 1024
> >
> > #define KVM_HALT_POLL_NS_DEFAULT 500000
> >
> > --
> > 2.25.1
> >
>
> Reviewed-by: Atish Patra <[email protected]>

Queued this patch for 5.19

Thanks,
Anup

>
> --
> Regards,
> Atish