On Fri, Aug 18, 2023 at 05:50:28AM -0400, Xiaoyao Li <xiaoyao.li@xxxxxxxxx> wrote: > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > If the range for TDG.VP.VMCALL<MapGPA> is too large, process the limited > size and return retry error. It's bad for VMM to take too long time, > e.g. second order, with blocking vcpu execution. It results in too many > missing timer interrupts. This patch requires the guest side patch. [1] Unless with large guest memory, it's unlikely to hit the limit with KVM/qemu, though. [1] https://lore.kernel.org/all/20230811021246.821-1-decui@xxxxxxxxxxxxx/ > > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx> > --- > target/i386/kvm/tdx.c | 19 ++++++++++++++++++- > 1 file changed, 18 insertions(+), 1 deletion(-) > > diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c > index 0c43c1f7759f..ced55be506d1 100644 > --- a/target/i386/kvm/tdx.c > +++ b/target/i386/kvm/tdx.c > @@ -994,12 +994,16 @@ static hwaddr tdx_shared_bit(X86CPU *cpu) > return (cpu->phys_bits > 48) ? BIT_ULL(51) : BIT_ULL(47); > } > > +/* 64MB at most in one call. What value is appropriate? */ > +#define TDX_MAP_GPA_MAX_LEN (64 * 1024 * 1024) > + > static void tdx_handle_map_gpa(X86CPU *cpu, struct kvm_tdx_vmcall *vmcall) > { > hwaddr shared_bit = tdx_shared_bit(cpu); > hwaddr gpa = vmcall->in_r12 & ~shared_bit; > bool private = !(vmcall->in_r12 & shared_bit); > hwaddr size = vmcall->in_r13; > + bool retry = false; > int ret = 0; > > vmcall->status_code = TDG_VP_VMCALL_INVALID_OPERAND; > @@ -1018,12 +1022,25 @@ static void tdx_handle_map_gpa(X86CPU *cpu, struct kvm_tdx_vmcall *vmcall) > return; > } > > + if (size > TDX_MAP_GPA_MAX_LEN) { > + retry = true; > + size = TDX_MAP_GPA_MAX_LEN; > + } > + > if (size > 0) { > ret = kvm_convert_memory(gpa, size, private); > } > > if (!ret) { > - vmcall->status_code = TDG_VP_VMCALL_SUCCESS; > + if (retry) { > + vmcall->status_code = TDG_VP_VMCALL_RETRY; > + vmcall->out_r11 = gpa + size; > + if (!private) { > + vmcall->out_r11 |= shared_bit; > + } > + } else { > + vmcall->status_code = TDG_VP_VMCALL_SUCCESS; > + } > } > } > > -- > 2.34.1 > > -- Isaku Yamahata <isaku.yamahata@xxxxxxxxxxxxxxx>
