| Message ID | ea28cfef061d06e86704845a877802e057749b39.1410302383.git.geoff@infradead.org (mailing list archive) |
|---|---|
| State | New, archived |
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On Tue, Sep 09, 2014 at 11:49:04PM +0100, Geoff Levand wrote: > Add the new hcall HVC_CALL_FUNC that allows execution of a function at EL2. > During CPU reset the CPU must be brought to the exception level it had on > entry to the kernel. The HVC_CALL_FUNC hcall will provide the mechanism > needed for this exception level switch. > > Signed-off-by: Geoff Levand <geoff@infradead.org> > --- > arch/arm64/include/asm/virt.h | 11 +++++++++++ > arch/arm64/kernel/hyp-stub.S | 10 ++++++++++ > 2 files changed, 21 insertions(+) [...] > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S > index 9ab5f70..a21cf51 100644 > --- a/arch/arm64/kernel/hyp-stub.S > +++ b/arch/arm64/kernel/hyp-stub.S > @@ -75,7 +75,17 @@ el1_sync: > 1: cmp x10, #HVC_SET_VECTORS > b.ne 1f > msr vbar_el2, x0 > + b 2f > > +1: cmp x10, #HVC_CALL_FUNC > + b.ne 1f > + mov x29, lr > + mov lr, x0 > + mov x0, x1 > + mov x1, x2 > + mov x2, x3 > + blr lr > + mov lr, x29 Why are you clobbering x29? Will
Hi Will, On Wed, 2014-09-10 at 18:07 +0100, Will Deacon wrote: > On Tue, Sep 09, 2014 at 11:49:04PM +0100, Geoff Levand wrote: > > Add the new hcall HVC_CALL_FUNC that allows execution of a function at EL2. > > During CPU reset the CPU must be brought to the exception level it had on > > entry to the kernel. The HVC_CALL_FUNC hcall will provide the mechanism > > needed for this exception level switch. > > > > Signed-off-by: Geoff Levand <geoff@infradead.org> > > --- > > arch/arm64/include/asm/virt.h | 11 +++++++++++ > > arch/arm64/kernel/hyp-stub.S | 10 ++++++++++ > > 2 files changed, 21 insertions(+) > > [...] > > > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S > > index 9ab5f70..a21cf51 100644 > > --- a/arch/arm64/kernel/hyp-stub.S > > +++ b/arch/arm64/kernel/hyp-stub.S > > @@ -75,7 +75,17 @@ el1_sync: > > 1: cmp x10, #HVC_SET_VECTORS > > b.ne 1f > > msr vbar_el2, x0 > > + b 2f > > > > +1: cmp x10, #HVC_CALL_FUNC > > + b.ne 1f > > + mov x29, lr > > + mov lr, x0 > > + mov x0, x1 > > + mov x1, x2 > > + mov x2, x3 > > + blr lr > > + mov lr, x29 > > Why are you clobbering x29? I can change this to x28, unless you can recommend another? -Geoff
On Wed, Sep 10, 2014 at 06:23:57PM +0100, Geoff Levand wrote: > On Wed, 2014-09-10 at 18:07 +0100, Will Deacon wrote: > > On Tue, Sep 09, 2014 at 11:49:04PM +0100, Geoff Levand wrote: > > > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S > > > index 9ab5f70..a21cf51 100644 > > > --- a/arch/arm64/kernel/hyp-stub.S > > > +++ b/arch/arm64/kernel/hyp-stub.S > > > @@ -75,7 +75,17 @@ el1_sync: > > > 1: cmp x10, #HVC_SET_VECTORS > > > b.ne 1f > > > msr vbar_el2, x0 > > > + b 2f > > > > > > +1: cmp x10, #HVC_CALL_FUNC > > > + b.ne 1f > > > + mov x29, lr > > > + mov lr, x0 > > > + mov x0, x1 > > > + mov x1, x2 > > > + mov x2, x3 > > > + blr lr > > > + mov lr, x29 > > > > Why are you clobbering x29? > > I can change this to x28, unless you can recommend another? How about something that's not callee saved? Will
On Tue, Sep 09, 2014 at 11:49:04PM +0100, Geoff Levand wrote: > Add the new hcall HVC_CALL_FUNC that allows execution of a function at EL2. > During CPU reset the CPU must be brought to the exception level it had on > entry to the kernel. The HVC_CALL_FUNC hcall will provide the mechanism > needed for this exception level switch. > > Signed-off-by: Geoff Levand <geoff@infradead.org> > --- > arch/arm64/include/asm/virt.h | 11 +++++++++++ > arch/arm64/kernel/hyp-stub.S | 10 ++++++++++ > 2 files changed, 21 insertions(+) > > diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h > index 894fe53..b217fbc 100644 > --- a/arch/arm64/include/asm/virt.h > +++ b/arch/arm64/include/asm/virt.h > @@ -41,6 +41,17 @@ > > #define HVC_KVM_CALL_HYP 3 > > +/* > + * HVC_CALL_FUNC - Execute a function at EL2. > + * > + * @x0: Physical address of the funtion to be executed. > + * @x1: Passed as the first argument to @fn. > + * @x2: Passed as the second argument to @fn. > + * @x3: Passed as the third argument to @fn. > + */ > + > +#define HVC_CALL_FUNC 4 > + Can't we use the HVC_KVM_CALL_HYP for this as well? I thought we already added the code to the stub to do that in the last patch. Is there a difference between the two that I'm missing? > #ifndef __ASSEMBLY__ > > /* > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S > index 9ab5f70..a21cf51 100644 > --- a/arch/arm64/kernel/hyp-stub.S > +++ b/arch/arm64/kernel/hyp-stub.S > @@ -75,7 +75,17 @@ el1_sync: > 1: cmp x10, #HVC_SET_VECTORS > b.ne 1f > msr vbar_el2, x0 > + b 2f > > +1: cmp x10, #HVC_CALL_FUNC > + b.ne 1f > + mov x29, lr What's the contract for functions we call through the stub? If they can use all the caller-saved registers, then we need to stach the original LR before issuing the HVC. Otherwise we can stash it in x18 at EL2. Thanks, Mark.
Hi Mark, On Mon, 2014-09-15 at 19:11 +0100, Mark Rutland wrote: > On Tue, Sep 09, 2014 at 11:49:04PM +0100, Geoff Levand wrote: > > Add the new hcall HVC_CALL_FUNC that allows execution of a function at EL2. > > During CPU reset the CPU must be brought to the exception level it had on > > entry to the kernel. The HVC_CALL_FUNC hcall will provide the mechanism > > needed for this exception level switch. > > > > Signed-off-by: Geoff Levand <geoff@infradead.org> > > --- > > arch/arm64/include/asm/virt.h | 11 +++++++++++ > > arch/arm64/kernel/hyp-stub.S | 10 ++++++++++ > > 2 files changed, 21 insertions(+) > > > > diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h > > index 894fe53..b217fbc 100644 > > --- a/arch/arm64/include/asm/virt.h > > +++ b/arch/arm64/include/asm/virt.h > > @@ -41,6 +41,17 @@ > > > > #define HVC_KVM_CALL_HYP 3 > > > > +/* > > + * HVC_CALL_FUNC - Execute a function at EL2. > > + * > > + * @x0: Physical address of the funtion to be executed. > > + * @x1: Passed as the first argument to @fn. > > + * @x2: Passed as the second argument to @fn. > > + * @x3: Passed as the third argument to @fn. > > + */ > > + > > +#define HVC_CALL_FUNC 4 > > + > > Can't we use the HVC_KVM_CALL_HYP for this as well? I thought we already > added the code to the stub to do that in the last patch. The last patch (arm64: Convert hcalls to use ISS field) only added function call support to the kvm vector. > Is there a difference between the two that I'm missing? The kvm and stub el1_sync vectors are different in that the kvm vector expects a stack to be set up whereas the stub vector does not. We have plenty of hcall numbers, so I thought it better to have two different numbers so improper usage would be easier to detect. > > #ifndef __ASSEMBLY__ > > > > /* > > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S > > index 9ab5f70..a21cf51 100644 > > --- a/arch/arm64/kernel/hyp-stub.S > > +++ b/arch/arm64/kernel/hyp-stub.S > > @@ -75,7 +75,17 @@ el1_sync: > > 1: cmp x10, #HVC_SET_VECTORS > > b.ne 1f > > msr vbar_el2, x0 > > + b 2f > > > > +1: cmp x10, #HVC_CALL_FUNC > > + b.ne 1f > > + mov x29, lr > > What's the contract for functions we call through the stub? My thinking was that this is just a mechanism to do the call. The caller and callee would need to set the conditions of the call. The only restriction is that the called function would need to preserve the register that lr is saved in (x29 here, but x18 in the current implementation). -Geoff
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h index 894fe53..b217fbc 100644 --- a/arch/arm64/include/asm/virt.h +++ b/arch/arm64/include/asm/virt.h @@ -41,6 +41,17 @@ #define HVC_KVM_CALL_HYP 3 +/* + * HVC_CALL_FUNC - Execute a function at EL2. + * + * @x0: Physical address of the funtion to be executed. + * @x1: Passed as the first argument to @fn. + * @x2: Passed as the second argument to @fn. + * @x3: Passed as the third argument to @fn. + */ + +#define HVC_CALL_FUNC 4 + #ifndef __ASSEMBLY__ /* diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S index 9ab5f70..a21cf51 100644 --- a/arch/arm64/kernel/hyp-stub.S +++ b/arch/arm64/kernel/hyp-stub.S @@ -75,7 +75,17 @@ el1_sync: 1: cmp x10, #HVC_SET_VECTORS b.ne 1f msr vbar_el2, x0 + b 2f +1: cmp x10, #HVC_CALL_FUNC + b.ne 1f + mov x29, lr + mov lr, x0 + mov x0, x1 + mov x1, x2 + mov x2, x3 + blr lr + mov lr, x29 1: 2: eret ENDPROC(el1_sync)
Add the new hcall HVC_CALL_FUNC that allows execution of a function at EL2. During CPU reset the CPU must be brought to the exception level it had on entry to the kernel. The HVC_CALL_FUNC hcall will provide the mechanism needed for this exception level switch. Signed-off-by: Geoff Levand <geoff@infradead.org> --- arch/arm64/include/asm/virt.h | 11 +++++++++++ arch/arm64/kernel/hyp-stub.S | 10 ++++++++++ 2 files changed, 21 insertions(+)