[Xen-devel] [PATCH 1/8] ppc/kvm: Replace ACCESS_ONCE with READ_ONCE

[Christian Borntraeger <borntraeger@xxxxxxxxxx>]

ACCESS_ONCE does not work reliably on non-scalar types. For
example gcc 4.6 and 4.7 might remove the volatile tag for such
accesses during the SRA (scalar replacement of aggregates) step
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145)

Change the ppc/kvm code to replace ACCESS_ONCE with READ_ONCE.

Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
 arch/powerpc/kvm/book3s_hv_rm_xics.c |  8 ++++----
 arch/powerpc/kvm/book3s_xics.c       | 16 ++++++++--------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_rm_xics.c 
b/arch/powerpc/kvm/book3s_hv_rm_xics.c
index 7b066f6..7c22997 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_xics.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_xics.c
@@ -152,7 +152,7 @@ static void icp_rm_down_cppr(struct kvmppc_xics *xics, 
struct kvmppc_icp *icp,
         * in virtual mode.
         */
        do {
-               old_state = new_state = ACCESS_ONCE(icp->state);
+               old_state = new_state = READ_ONCE(icp->state);
 
                /* Down_CPPR */
                new_state.cppr = new_cppr;
@@ -211,7 +211,7 @@ unsigned long kvmppc_rm_h_xirr(struct kvm_vcpu *vcpu)
         * pending priority
         */
        do {
-               old_state = new_state = ACCESS_ONCE(icp->state);
+               old_state = new_state = READ_ONCE(icp->state);
 
                xirr = old_state.xisr | (((u32)old_state.cppr) << 24);
                if (!old_state.xisr)
@@ -277,7 +277,7 @@ int kvmppc_rm_h_ipi(struct kvm_vcpu *vcpu, unsigned long 
server,
         * whenever the MFRR is made less favored.
         */
        do {
-               old_state = new_state = ACCESS_ONCE(icp->state);
+               old_state = new_state = READ_ONCE(icp->state);
 
                /* Set_MFRR */
                new_state.mfrr = mfrr;
@@ -352,7 +352,7 @@ int kvmppc_rm_h_cppr(struct kvm_vcpu *vcpu, unsigned long 
cppr)
        icp_rm_clr_vcpu_irq(icp->vcpu);
 
        do {
-               old_state = new_state = ACCESS_ONCE(icp->state);
+               old_state = new_state = READ_ONCE(icp->state);
 
                reject = 0;
                new_state.cppr = cppr;
diff --git a/arch/powerpc/kvm/book3s_xics.c b/arch/powerpc/kvm/book3s_xics.c
index 807351f..a4a8d9f 100644
--- a/arch/powerpc/kvm/book3s_xics.c
+++ b/arch/powerpc/kvm/book3s_xics.c
@@ -327,7 +327,7 @@ static bool icp_try_to_deliver(struct kvmppc_icp *icp, u32 
irq, u8 priority,
                 icp->server_num);
 
        do {
-               old_state = new_state = ACCESS_ONCE(icp->state);
+               old_state = new_state = READ_ONCE(icp->state);
 
                *reject = 0;
 
@@ -512,7 +512,7 @@ static void icp_down_cppr(struct kvmppc_xics *xics, struct 
kvmppc_icp *icp,
         * in virtual mode.
         */
        do {
-               old_state = new_state = ACCESS_ONCE(icp->state);
+               old_state = new_state = READ_ONCE(icp->state);
 
                /* Down_CPPR */
                new_state.cppr = new_cppr;
@@ -567,7 +567,7 @@ static noinline unsigned long kvmppc_h_xirr(struct kvm_vcpu 
*vcpu)
         * pending priority
         */
        do {
-               old_state = new_state = ACCESS_ONCE(icp->state);
+               old_state = new_state = READ_ONCE(icp->state);
 
                xirr = old_state.xisr | (((u32)old_state.cppr) << 24);
                if (!old_state.xisr)
@@ -634,7 +634,7 @@ static noinline int kvmppc_h_ipi(struct kvm_vcpu *vcpu, 
unsigned long server,
         * whenever the MFRR is made less favored.
         */
        do {
-               old_state = new_state = ACCESS_ONCE(icp->state);
+               old_state = new_state = READ_ONCE(icp->state);
 
                /* Set_MFRR */
                new_state.mfrr = mfrr;
@@ -679,7 +679,7 @@ static int kvmppc_h_ipoll(struct kvm_vcpu *vcpu, unsigned 
long server)
                if (!icp)
                        return H_PARAMETER;
        }
-       state = ACCESS_ONCE(icp->state);
+       state = READ_ONCE(icp->state);
        kvmppc_set_gpr(vcpu, 4, ((u32)state.cppr << 24) | state.xisr);
        kvmppc_set_gpr(vcpu, 5, state.mfrr);
        return H_SUCCESS;
@@ -721,7 +721,7 @@ static noinline void kvmppc_h_cppr(struct kvm_vcpu *vcpu, 
unsigned long cppr)
                                      BOOK3S_INTERRUPT_EXTERNAL_LEVEL);
 
        do {
-               old_state = new_state = ACCESS_ONCE(icp->state);
+               old_state = new_state = READ_ONCE(icp->state);
 
                reject = 0;
                new_state.cppr = cppr;
@@ -885,7 +885,7 @@ static int xics_debug_show(struct seq_file *m, void 
*private)
                if (!icp)
                        continue;
 
-               state.raw = ACCESS_ONCE(icp->state.raw);
+               state.raw = READ_ONCE(icp->state.raw);
                seq_printf(m, "cpu server %#lx XIRR:%#x PPRI:%#x CPPR:%#x 
MFRR:%#x OUT:%d NR:%d\n",
                           icp->server_num, state.xisr,
                           state.pending_pri, state.cppr, state.mfrr,
@@ -1082,7 +1082,7 @@ int kvmppc_xics_set_icp(struct kvm_vcpu *vcpu, u64 icpval)
         * the ICS states before the ICP states.
         */
        do {
-               old_state = ACCESS_ONCE(icp->state);
+               old_state = READ_ONCE(icp->state);
 
                if (new_state.mfrr <= old_state.mfrr) {
                        resend = false;
-- 
1.9.3


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