On 2015/9/3 0:08, Christoffer Dall wrote: > On Mon, Aug 10, 2015 at 09:26:07PM +0800, Zhichao Huang wrote: >> Enable trapping of the debug registers unconditionally, allowing guests to >> use the debug infrastructure. >> >> Signed-off-by: Zhichao Huang <zhichao.hu...@linaro.org> >> Reviewed-by: Christoffer Dall <christoffer.d...@linaro.org> >> --- >> arch/arm/kvm/interrupts_head.S | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S >> index 7ad0adf..494991d 100644 >> --- a/arch/arm/kvm/interrupts_head.S >> +++ b/arch/arm/kvm/interrupts_head.S >> @@ -792,7 +792,7 @@ ARM_BE8(rev r6, r6 ) >> * (hardware reset value is 0) */ >> .macro set_hdcr operation >> mrc p15, 4, r2, c1, c1, 1 >> - ldr r3, =(HDCR_TPM|HDCR_TPMCR) >> + ldr r3, =(HDCR_TPM|HDCR_TPMCR|HDCR_TDRA|HDCR_TDOSA|HDCR_TDA) > > eh, but I thought we didn't have to trap accesses to the debug registers > if we switch them, because the guest is likely to be using them? > > Maybe I am getting confused, can you repeat for me exactly when we > context-switch the registers and when we trap accesses to them? >
Since we don't want to world switch the dangerous register(DBGDSCR), we have to trap accesses all the time, to prevent the guest to write to the real register. > Thanks, > -Christoffer > >> .if \operation == vmentry >> orr r2, r2, r3 @ Trap some perfmon accesses >> .else >> -- >> 1.7.12.4 >> -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
