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[kernel] Set framebuffer to write-combining

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Several changes were needed to make this work:

- Update the page_table::flags to understand memory caching types
- Set up the PAT MSR to add the WC option
- Make page-offset area mapped as WT
- Add all the MTRR and PAT MSRs, and log the MTRRs for verification
- Add a vm_area flag for write_combining
This commit is contained in:
Justin C. Miller
2021-01-17 20:49:47 -08:00
parent 1820972fb7
commit 3dffe564af
10 changed files with 152 additions and 38 deletions
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66
src/kernel/memory_bootstrap.cpp
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@@ -9,6 +9,7 @@
#include "frame_allocator.h"
#include "io.h"
#include "log.h"
#include "msr.h"
#include "objects/process.h"
#include "objects/vm_area.h"
#include "vm_space.h"
@@ -100,6 +101,71 @@ void walk_page_table(
}
*/
static void
log_mtrrs()
{
uint64_t mtrrcap = rdmsr(msr::ia32_mtrrcap);
uint64_t mtrrdeftype = rdmsr(msr::ia32_mtrrdeftype);
unsigned vcap = mtrrcap & 0xff;
log::debug(logs::boot, "MTRRs: vcap=%d %s %s def=%02x %s %s",
vcap,
(mtrrcap & (1<< 8)) ? "fix" : "",
(mtrrcap & (1<<10)) ? "wc" : "",
mtrrdeftype & 0xff,
(mtrrdeftype & (1<<10)) ? "fe" : "",
(mtrrdeftype & (1<<11)) ? "enabled" : ""
);
for (unsigned i = 0; i < vcap; ++i) {
uint64_t base = rdmsr(find_mtrr(msr::ia32_mtrrphysbase, i));
uint64_t mask = rdmsr(find_mtrr(msr::ia32_mtrrphysmask, i));
log::debug(logs::boot, " vcap[%2d] base:%016llx mask:%016llx type:%02x %s", i,
(base & ~0xfffull),
(mask & ~0xfffull),
(base & 0xff),
(mask & (1<<11)) ? "valid" : "");
}
msr mtrr_fixed[] = {
msr::ia32_mtrrfix64k_00000,
msr::ia32_mtrrfix16k_80000,
msr::ia32_mtrrfix16k_a0000,
msr::ia32_mtrrfix4k_c0000,
msr::ia32_mtrrfix4k_c8000,
msr::ia32_mtrrfix4k_d0000,
msr::ia32_mtrrfix4k_d8000,
msr::ia32_mtrrfix4k_e0000,
msr::ia32_mtrrfix4k_e8000,
msr::ia32_mtrrfix4k_f0000,
msr::ia32_mtrrfix4k_f8000,
};
for (int i = 0; i < 11; ++i) {
uint64_t v = rdmsr(mtrr_fixed[i]);
log::debug(logs::boot, " fixed[%2d] %02x %02x %02x %02x %02x %02x %02x %02x", i,
((v << 0) & 0xff), ((v << 8) & 0xff), ((v << 16) & 0xff), ((v << 24) & 0xff),
((v << 32) & 0xff), ((v << 40) & 0xff), ((v << 48) & 0xff), ((v << 56) & 0xff));
}
uint64_t pat = rdmsr(msr::ia32_pat);
static const char *pat_names[] = {"UC ","WC ","XX ","XX ","WT ","WP ","WB ","UC-"};
log::debug(logs::boot, " PAT: 0:%s 1:%s 2:%s 3:%s 4:%s 5:%s 6:%s 7:%s",
pat_names[(pat >> (0*8)) & 7], pat_names[(pat >> (1*8)) & 7],
pat_names[(pat >> (2*8)) & 7], pat_names[(pat >> (3*8)) & 7],
pat_names[(pat >> (4*8)) & 7], pat_names[(pat >> (5*8)) & 7],
pat_names[(pat >> (6*8)) & 7], pat_names[(pat >> (7*8)) & 7]);
}
void
setup_pat()
{
uint64_t pat = rdmsr(msr::ia32_pat);
pat = (pat & 0x00ffffffffffffffull) | (0x01ull << 56); // set PAT 7 to WC
wrmsr(msr::ia32_pat, pat);
log_mtrrs();
}
void
memory_initialize_pre_ctors(args::header *kargs)
{