x86/apic: Add an update_vector() callback for Secure AVIC

Add an update_vector() callback to set/clear the ALLOWED_IRR field in a vCPU's
APIC backing page for vectors which are emulated by the hypervisor.

The ALLOWED_IRR field indicates the interrupt vectors which the guest allows
the hypervisor to inject (typically for emulated devices).  Interrupt vectors
used exclusively by the guest itself and the vectors which are not emulated by
the hypervisor, such as IPI vectors, should not be set by the guest in the
ALLOWED_IRR fields.

As clearing/setting state of a vector will also be used in subsequent commits
for other APIC registers (such as APIC_IRR update for sending IPI), add
a common update_vector() in the Secure AVIC driver.

  [ bp: Massage commit message. ]

Co-developed-by: Kishon Vijay Abraham I <kvijayab@amd.com>
Signed-off-by: Kishon Vijay Abraham I <kvijayab@amd.com>
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Link: https://lore.kernel.org/20250828110255.208779-4-Neeraj.Upadhyay@amd.com

diff --git a/arch/x86/kernel/apic/x2apic_savic.c b/arch/x86/kernel/apic/x2apic_savic.c
index 56c51ea4e5ab7bce7ebb0aaa43dbad9c18515d00..942d3aa25082b686ef78da05665524ddd539993f 100644 (file)
--- a/arch/x86/kernel/apic/x2apic_savic.c
+++ b/arch/x86/kernel/apic/x2apic_savic.c
@@ -27,6 +27,22 @@ static int savic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
        return x2apic_enabled() && cc_platform_has(CC_ATTR_SNP_SECURE_AVIC);
 }
 
+static inline void *get_reg_bitmap(unsigned int cpu, unsigned int offset)
+{
+       return &per_cpu_ptr(savic_page, cpu)->regs[offset];
+}
+
+static inline void update_vector(unsigned int cpu, unsigned int offset,
+                                unsigned int vector, bool set)
+{
+       void *bitmap = get_reg_bitmap(cpu, offset);
+
+       if (set)
+               apic_set_vector(vector, bitmap);
+       else
+               apic_clear_vector(vector, bitmap);
+}
+
 #define SAVIC_ALLOWED_IRR      0x204
 
 /*
@@ -144,6 +160,11 @@ static void savic_write(u32 reg, u32 data)
        }
 }
 
+static void savic_update_vector(unsigned int cpu, unsigned int vector, bool set)
+{
+       update_vector(cpu, SAVIC_ALLOWED_IRR, vector, set);
+}
+
 static void savic_setup(void)
 {
        void *ap = this_cpu_ptr(savic_page);
@@ -217,6 +238,8 @@ static struct apic apic_x2apic_savic __ro_after_init = {
        .eoi                            = native_apic_msr_eoi,
        .icr_read                       = native_x2apic_icr_read,
        .icr_write                      = native_x2apic_icr_write,
+
+       .update_vector                  = savic_update_vector,
 };
 
 apic_driver(apic_x2apic_savic);