platform: Add abstractions for request processing

Add new abstractions to SvsmPlatform:

- request_task() is the kernel task for request processing
- request_loop() is the main vCPU request loop

Only SEV-SNP platforms do useful things in their implementations right
now.

Signed-off-by: Peter Fang <[email protected]>

kernel/src/cpu/smp.rs

@@ -13,7 +13,7 @@ use crate::cpu::shadow_stack::{is_cet_ss_supported, SCetFlags, MODE_64BIT, S_CET
 use crate::cpu::sse::sse_init;
 use crate::enable_shadow_stacks;
 use crate::error::SvsmError;
-use crate::platform::{request_loop, request_processing_main, SvsmPlatform, SVSM_PLATFORM};
+use crate::platform::{request_task_main, SvsmPlatform, SVSM_PLATFORM};
 use crate::task::{schedule_init, start_kernel_task};
 use crate::utils::immut_after_init::immut_after_init_set_multithreaded;
 
@@ -72,8 +72,8 @@ fn start_ap() {
 
 #[no_mangle]
 pub extern "C" fn ap_request_loop() {
-    start_kernel_task(request_processing_main, String::from("request-processing"))
+    start_kernel_task(request_task_main, String::from("request-processing"))
         .expect("Failed to launch request processing task");
-    request_loop();
+    SVSM_PLATFORM.request_loop();
     panic!("Returned from request_loop!");
 }

kernel/src/platform/mod.rs

@@ -12,7 +12,6 @@ pub mod tdp;
 mod snp_fw;
 mod snp_requests;
 pub use snp_fw::{parse_fw_meta_data, SevFWMetaData};
-pub use snp_requests::{request_loop, request_processing_main};
 
 use native::NativePlatform;
 use snp::SnpPlatform;
@@ -168,6 +167,12 @@ pub trait SvsmPlatform {
         cpu: &PerCpu,
         context: &hyperv::HvInitialVpContext,
     ) -> Result<(), SvsmError>;
+
+    /// Entry point for the kernel request task.
+    fn request_task(&self) {}
+
+    /// Enter the main vCPU loop.
+    fn request_loop(&self);
 }
 
 //FIXME - remove Copy trait
@@ -225,3 +230,7 @@ pub fn halt() {
         SvsmPlatformType::Tdp => TdpPlatform::halt(),
     }
 }
+
+pub extern "C" fn request_task_main() {
+    SVSM_PLATFORM.request_task();
+}

kernel/src/platform/native.rs

@@ -173,4 +173,6 @@ impl SvsmPlatform for NativePlatform {
 
         todo!();
     }
+
+    fn request_loop(&self) {}
 }

kernel/src/platform/snp.rs

@@ -7,6 +7,7 @@
 use super::snp_fw::{
     copy_tables_to_fw, launch_fw, prepare_fw_launch, print_fw_meta, validate_fw, validate_fw_memory,
 };
+use super::{snp_requests, PageEncryptionMasks, PageStateChangeOp, PageValidateOp, SvsmPlatform};
 use crate::address::{Address, PhysAddr, VirtAddr};
 use crate::config::SvsmConfig;
 use crate::console::init_svsm_console;
@@ -19,7 +20,6 @@ use crate::hyperv;
 use crate::io::IOPort;
 use crate::mm::memory::write_guest_memory_map;
 use crate::mm::{PerCPUPageMappingGuard, PAGE_SIZE, PAGE_SIZE_2M};
-use crate::platform::{PageEncryptionMasks, PageStateChangeOp, PageValidateOp, SvsmPlatform};
 use crate::sev::ghcb::GHCBIOSize;
 use crate::sev::hv_doorbell::current_hv_doorbell;
 use crate::sev::msr_protocol::{
@@ -330,6 +330,14 @@ impl SvsmPlatform for SnpPlatform {
 
         current_ghcb().ap_create(vmsa_pa, cpu.get_apic_id().into(), 0, sev_features)
     }
+
+    fn request_task(&self) {
+        snp_requests::request_processing_main();
+    }
+
+    fn request_loop(&self) {
+        snp_requests::request_loop();
+    }
 }
 
 #[derive(Clone, Copy, Debug, Default)]

kernel/src/platform/snp_requests.rs

@@ -184,8 +184,7 @@ pub fn request_loop() {
     }
 }
 
-#[no_mangle]
-pub extern "C" fn request_processing_main() {
+pub fn request_processing_main() {
     let apic_id = this_cpu().get_apic_id();
 
     log::info!("Launching request-processing task on CPU {}", apic_id);

kernel/src/platform/tdp.rs

@@ -183,6 +183,10 @@ impl SvsmPlatform for TdpPlatform {
     ) -> Result<(), SvsmError> {
         todo!();
     }
+
+    fn request_loop(&self) {
+        todo!();
+    }
 }
 
 #[derive(Clone, Copy, Debug, Default)]

kernel/src/svsm.rs

@@ -40,9 +40,7 @@ use svsm::mm::pagetable::paging_init;
 use svsm::mm::virtualrange::virt_log_usage;
 use svsm::mm::{init_kernel_mapping_info, FixedAddressMappingRange};
 use svsm::platform;
-use svsm::platform::{
-    init_platform_type, request_loop, request_processing_main, SvsmPlatformCell, SVSM_PLATFORM,
-};
+use svsm::platform::{init_platform_type, request_task_main, SvsmPlatformCell, SVSM_PLATFORM};
 use svsm::sev::secrets_page_mut;
 use svsm::svsm_paging::{init_page_table, invalidate_early_boot_memory};
 use svsm::task::exec_user;
@@ -324,7 +322,7 @@ pub extern "C" fn svsm_main() {
         panic!("Failed to launch FW: {e:#?}");
     }
 
-    start_kernel_task(request_processing_main, String::from("request-processing"))
+    start_kernel_task(request_task_main, String::from("request-processing"))
         .expect("Failed to launch request processing task");
 
     #[cfg(test)]
@@ -335,7 +333,7 @@ pub extern "C" fn svsm_main() {
         Err(e) => log::info!("Failed to launch /init: {e:#?}"),
     }
 
-    request_loop();
+    SVSM_PLATFORM.request_loop();
 
     panic!("Road ends here!");
 }